Forensic Science Flashcards

Criminal Justice and Forensic Science

Chapter 1: Introduction

• Forensic science is a wide-ranging field with a rich history that is often untapped.
• A lack of historical knowledge can lead to repeating past mistakes, highlighting the importance of understanding the field's history.
• Forensic science occupies a unique position between law enforcement and the courts, requiring practitioners to balance pressures from both sides while adhering to scientific tenets.
• It's considered a growth industry with abundant material and promising technological advancements.

Key Terms:

• American Society for Testing and Materials, International (ASTM)
• American Society of Crime Laboratory Directors (ASCLD)
• ASCLD Laboratory Accreditation Board (ASCLD-LAB)
• Behavioral sciences
• Chain of custody
• Criminalistics
• Criminalists
• Forensic anthropology
• Forensic engineering
• Forensic odontology
• Forensic pathology
• Forensic science
• Forensic Science Education Programs Accreditation Commission (FEPAC)
• International Organization for Standardization (ISO)
• Questioned documents
• Technical Working Group on Education and Training in Forensic Science (TWGED)
• Toxicology

What Is Forensic Science?

• The term "forensic science" was first used to describe a "mixed science" that applied science to legal questions.
• It has evolved into a profession and a science in its own right.
• Forensic science is the science of associating people, places, and things involved in criminal activities; these scientific disciplines assist in investigating and adjudicating criminal and civil cases.
• "Science" refers to systematic methodologies used to understand the physical world.
• "Forensic" comes from the Latin word "forum," meaning "public," and technically means "as applied to public or legal concerns."
• Forensic scientists provide answers to courts through reports and testimony.

Criminalistics and Trace Evidence

• Criminalistics is sometimes used synonymously with forensic science but is the application of scientific and technological methods to legal investigations.
• In some labs, forensic scientists are called criminalists.
• Criminalistics involves collecting and analyzing physical evidence from criminal activity, such as drugs, firearms, fingerprints, blood, footwear, and trace evidence.
• Trace evidence includes fire and explosive residues, glass, soils, hairs, fibers, paints, plastics, wood, metals, and chemicals.
• The textbook uses "forensic sciences" and "forensic scientists" instead of "criminalistics" and "criminalist" to avoid confusion.

Areas of Forensic Science

• Forensic science is divided into chemical, biological, and physical sciences, with some overlap.
• The textbook organizes topics based on their original source or production method.
• Various specialists, such as artists, biologists, and chemists, may be needed for investigations like mass disasters, aeroplane crashes, missing persons, and art forgeries.

Birds of a Forensic Feather

• Forensic feather identification helped determine the cause of the US Airways Flight 1549 crash landing in the Hudson River in 2009.
• Dr. Carla Dove at the Smithsonian Institution's Feather Identification Laboratory identifies bird remains from aeroplane collisions.
• Feathers are compared with an extensive reference collection (over 620,000 samples) to determine the bird's species.
• DNA analysis is used if feather comparison is inconclusive.
• Avian anatomy knowledge is essential, as shown in the case where deer DNA on a plane was traced to a black vulture with deer flesh in its stomach.
• The lab has been analyzing bird remains from aeroplane crashes since 1960 and also works on military crashes.
• Forensic feather analysis will become more important due to climate change affecting bird distributions.

A Bit of Forensic Science History

• Forensic medicine was practiced as early as the fifth century.
• Toxicology emerged as one of the first "new" forensic sciences.
• In 1840, Mathieu Orfilia determined that Mr. Lefarge had ingested arsenic, leading to his wife's conviction.
• The eighteenth and nineteenth centuries saw advances in personal identification.
• Alphonse Bertillon developed anthropometry (Bertillonage), a method of recording physical features for unique identification.
• The Bertillon system became popular but was discredited after the William West case in 1903, where two men with the same name had virtually the same measurements.
• Dr. Juan Vucetich conceived of a fingerprint classification method in 1894.
• Sir William Herschel and Henry Faulds studied fingerprints for identification in India and Scotland.
• In 1901, Sir Edward Henry devised a fingerprint classification system still used today.
• Alexandre Lacassagne and Edmund Locard established practical and philosophical foundations for forensic sciences; Located started the world’s first forensic science laboratory in 1910.
• Karl Landsteiner discovered the ABO blood typing system around 1900, leading to forensic typing of blood.
• Sir Alec Jeffries developed the first forensic DNA typing method, "DNA fingerprinting," in 1984; the work Kary Mullis, led to the polymerase chain reaction (PCR).
• In the early twentieth century, Goddard popularized the comparison microscope.
• Professional forensic organizations, such as the American Academy of Forensic Sciences, help forensic scientists stay current.

Forensic Science Laboratory Organization and Services

• There is no single structure for forensic science laboratory organization; it varies by jurisdiction, agency, and history.
• The services offered by a lab depend on budget, personnel, equipment, and crime statistics.
• The following sections focus on the laboratories in the United States and answer two questions: How is a laboratory administered? What services does a laboratory provide?

Forensic Science Laboratory Administration

• The vast majority of forensic science laboratories in the United States are public, financed and operated by government units.
• There are also an undetermined number of private forensic science laboratories.

Private Forensic Science Laboratories

• Most private labs serve a niche, performing one or two examinations like drugs, toxicology, or questioned documents.
• Many are one-person operations run by retired forensic scientists.
• A significant number of private labs are devoted to DNA analysis for criminal or civil cases (paternity testing).
• Private labs provide services directly to persons accused of crimes, while public labs usually serve only law enforcement.
• Some public labs accept evidence from private citizens with fees subsidized by the jurisdiction.

Public Forensic Science Laboratories

• Public labs are administered and financed by a unit of government, varying by jurisdiction.
• The federal government, states, and local entities have different models.
• The Bureau of Justice Statistics conducts censuses on public labs to understand the industry.
• A 2012 census revealed troubling facts:
  • Nearly 1.2 million cases were backlogged at the end of 2009.
  • Forensic biology accounted for one-third of requests but three-quarters of the backlog.
  • One-third of laboratories sent casework to a private laboratory to try to stay current in their work.
• The census also showed positive trends:
  • Over 80% of public labs are accredited.
  • Over 80% have a laboratory information management system.
  • The number of forensic scientists rose to over 13,000.
• The FORESIGHT Project, funded by the National Institute of Justice (NIJ), collects standardized business measures from volunteer labs to benchmark effectiveness.
• This allows labs to self-evaluate and allocate resources efficiently.
• The FORESIGHT Project provides descriptive statistics on costs per case and cases worked per full-time employee.

Federal Government Forensic Science Laboratories

• The FBI Laboratory is the most famous but not the only federal forensic science laboratory.
• The Department of Justice:
  • The FBI has a laboratory and a research center in Quantico, Virginia.
  • The FBI laboratory supports its investigative efforts and analyzes evidence for state and local agencies.
  • The Drug Enforcement Administration (DEA) has seven drug laboratories and a research laboratory, supporting DEA and local law enforcement efforts.
  • The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has three regional laboratories and a fire research laboratory with expertise in fire scene analysis and explosives.
• Department of Homeland Security (DHS):
  • The Secret Service Laboratory handles counterfeiting and fraud cases, maintaining a large library of ink standards and offering questioned document analysis.
  • The Secret Service laboratory researches countermeasures and protection for the president and other officials.
• The Department of the Interior:
  • The US Fish and Wildlife Service operates a forensic science laboratory in Ashland, Oregon.
  • This lab supports investigations of poaching and wildlife crimes, specializing in identifying animal tissues and consulting on animal trafficking cases.
• US Postal Service
  • The Postal Service maintains a laboratory that supports the service’s efforts to combat postal fraud. This effort mainly involves questioned document analysis although the laboratory also has fingerprint and trace evidence capabilities.
• Additional federal laboratories include the Department of Defense, Customs and Border Patrol (DHS) and Department of the Treasury.

State and Local Forensic Science Laboratories

• Every state in the United States maintains at least one forensic science laboratory.
• There is no nationwide effort to standardize laboratory organization or function.
• Laboratories arise from law enforcement agencies or health departments.
• Some states, like Michigan, merged state police and health department laboratories to combine expertise.
• Most states have a statewide laboratory system operated by the state police, department of justice, or as an independent system, as in Virginia.
• California has an extensive network of state-financed laboratories, while West Virginia has a single laboratory.
• Besides statewide systems, local governments operate laboratories in some states, for example, the county police department in Maryland.
• In Texas, some police or sheriffs' departments in major cities operate city laboratories, as in Fort Worth.
• Los Angeles has a county and a city laboratory.
• The District of Columbia has a local laboratory serving the D.C. Metropolitan Police Department and federal agencies.
• This patchwork of jurisdictions is maintained due to societal needs, such as population levels, crime rates, and geography.

Forensic Science Laboratory Services

• Laboratories offer different service levels; statewide systems may have a full-service headquarters and limited-service regional laboratories.
• A "full service" designation may vary between states.

• Evidence Intake
  • All labs have an evidence intake system with secured storage; the size depends on the volume of evidence and casework.
  • Police officers or investigators bring evidence to the laboratory with a form describing the evidence and requested examinations.
  • A unique laboratory number is assigned to the case, and each item is labeled with this number and identifying information.
  • This begins the chain of custody, documenting who had what items of evidence and when.
  • The evidence intake unit functions like inventory control for a business.
  • Modern systems use computerized systems with barcodes for easy tracing.
  • Paperwork accompanies the evidence, and each analyst signs or accepts possession.
• Analytical Sections
  • Once the evidence has been received by the laboratory, it will be assigned to one or more forensic units for analysis
  • More than one scientist may be asked to analyze an item of evidence, and then arrangements must be made to get the evidence to each scientist in a logical order.
  • Examinations must be performed in an order that will not disrupt or destroy any of the evidence on the gun.
  • In some laboratories, one forensic scientist may be certified to examine several of these evidence types; in larger laboratories that have the luxury of specialization, a scientist may examine only one or two.

• Some laboratories offer additional services depending on needs and qualified scientists.
• These may include bloodstain pattern analysis, entomology, odontology, and anthropology.

Administrative Issues with Forensic Science Laboratories

• Laboratories face increasing demands, workloads, and scrutiny.
• Two major administrative issues are accountability and access.

• There is no mandatory accreditation process for forensic science laboratories in the United States, unlike hospitals and environmental companies.
• This is partly due to labs arising within police agencies.
• Movements to accredit forensic science laboratories have had some success, with over 80% seeking voluntary accreditation, and some states requiring it.
• The standard for accreditation is ISO 17025 General requirements for the competence of testing and calibration laboratories.
• Accreditation involves self-study, a checklist of requirements, and an on-site evaluation.
• Accreditation means that the laboratory meets certain minimum criteria for the physical plant, security, training, equipment, quality assurance and control, and other essential features.
• Reaccreditation is required every 5 years.
• The American Society for Testing and Materials, International (ASTM), publishes voluntary consensus standards for forensic science.

• Most forensic science laboratories in the United States are publicly funded and support government agencies.
• Police officers, detectives, crime scene investigators, and prosecutors generally have open access to the services of the laboratory, including expert testimony by its forensic sciences at no cost to the other agency.
• Accused citizens, however, have limited access, even if willing to pay.
• Limited options include private labs, but costs are high, and courts may not authorize funds for indigent defendants.
• Public defenders' offices often lack sufficient funds for evidence analysis.
• This results in an imbalance in resources between prosecution and defense.
• One recommendation is that forensic laboratories should be independent from law enforcement.

• Forensic service providers play a necessary role in the criminal justice system.
• The stakeholders included governmental ones, including law enforcement, attorneys and the courts
• Many forensic labs are administratively part of law enforcement agencies, which can affect their relationships with parent and aligned agencies.
• Some laboratories are overseen by sworn officers with no science education or training, affecting resource management.
• In 2009, the National Academy of Sciences recommended that forensic service providers be administratively or financially independent of law enforcement agencies.
• Concerns were raised about political clout, oversight, investigation participation, and potential gains or losses through independence.
• Some jurisdictions have created independent forensic agencies, such as Washington, D.C.'s Department of Forensic Sciences and Houston Forensic Science, LGC in Texas.
• Their vision was for the laboratory director to have a voice equivalent with or at least proportional to others in the jurisdiction and the justice system on matters involving the laboratory and related agencies.
• The committee felt that the laboratory should also be able to establish and maintain prioritization of cases, expenditures and other resources while also having budgetary autonomy to set its own financial goals.
• Establishing separate entities aims to mitigate pressures related to differing goals between laboratories and law enforcement.
• Independence is not a cure-all, as seen in the Annie Dookhan case in Massachusetts.
• Removing labs from law enforcement oversight addresses the 'fox guarding the hen house' issue.
• It remains to be seen whether these “independent” laboratories will remain so or if political interference pushes aside the objectivity of science for prosecutorial gains.
• The need for strategic leadership in forensic science is critical and the lack of a historical systems-level view has slowed the development of strong strategic leadership.
• Forensic service providers, traditionally under law enforcement agencies, have had few opportunities to have a collective, distinctive political voice that served them alone.

The Forensic Scientist

• Forensic scientists analyze evidence and offer expert testimony.
• Other responsibilities include training in evidence collection, research, and method validation.

• Science is central to forensic science, reinforced by court decisions.
• Forensic scientists must be versed in scientific methods, specific techniques, rules of evidence, and court procedures.
• This is gained through education, training, and experience.

• Historically, forensic scientists were chemistry or biology majors.
• Since the mid-twentieth century, colleges and universities have offered forensic science programs.
• Early bachelor's programs included science backgrounds, lab experience, and classes in law and criminal procedure.
• Graduate degrees, particularly master's, have become the norm.
• They require a science bachelor's degree and teach applications of science to forensic work, law, criminal investigation, and justice, as well as research.
• The American Academy of Forensic Sciences (AAFS) initiated the Forensic Science Education Programs Accreditation Commission (FEPAC).
• FEPAC maintains and enhances the quality of forensic science education through formal evaluation and recognition of college-level academic programs.
• In 2009, FEPAC began a process for programs offering degrees in digital evidence and computer forensic investigation.
• Education programs do not provide enough training; graduates cannot start working cases immediately.

• Scientists hired by a lab begin formal training as specialists in areas like drug analysis, DNA analysis, or firearms examination.
• Training involves apprenticeship with experienced scientists.
• Training duration varies by discipline and laboratory.
• Drug chemists may train for 3 – 6 months, DNA analysts longer, and questioned document examiners a year or more.
• Training includes mock casework, assisting in real cases, proficiency testing, and mock trials.

• Laboratories train new employees in the technical and administrative aspects specific to that agency.
• Each case is a project of sorts and managing time and resources is a new experience for many new employees.
• The pressures of testifying in court must be managed, the “hurry up and wait” of testifying, the media (possibly) and dealing with harried attorneys are all important skills not taught in college courses.

• The science and method of the analysis process is important
• The forensic scientist must be constantly aware of the requirements of the chain of custody. Evidence can be rendered inadmissible if the chain of custody is not properly constructed and maintained.
• There are federal and state “speedy trial” laws that require an accused person be brought to trial within a specified window of time after arrest
• Forensic scientists have a duty to preserve as much of the evidence as is practical in each case and to ensure that the evidence is not spoiled or ruined.
• In many cases there is so much evidence that sampling becomes an issue.
• Every laboratory has protocols for writing laboratory reports, but a surprising lack of uniformity exists from laboratory to laboratory.

• Being a competent analytical scientist is only half the battle in a forensic science laboratory.
• The forensic scientist must also be able to explain his or her findings to a judge or jury in a court of law.
• This is one of the key factors that distinguish careers in forensic science from those in other sciences.
• An expert may be thought of as a person who possesses a combination of knowledge, skills, and abilities in a particular area that permit him or her to draw inferences from facts that the average person would not be competent to do.
• An expert knows more about something than the average person and has the credentials to prove it.
• A difference exists, however, between an expert and a forensic scientist: A mechanic is not a forensic scientist.

Chapter 2: Crime Scene Investigation

Abstract

• The crime scene is the center of the forensic world.
• The importance of a carefully processed crime scene cannot be overstated..
• The processing of a crime scene is a one-way street; there is no going back.
• Standard operating procedures and protocols guide the crime scene investigator, but training, experience, and education all play a role in adapting to each unique crime scene.

Key Terms:

• Artifact
• Bloodborne pathogens (BBPs)
• Context
• Crime scene investigator (CSI)
• Datum
• Feature
• Material safety data sheet (MSDS)
• Organic or environmental remains
• Provenance
• Universal precautions

Introduction

• Crime Scene Investigation deals with the transformation of the mundane into that special category called “evidence.”
• The importance of a properly processed crime scene cannot be overemphasized—and yet, it is where devastating mistakes occur that affect an entire case.
• Many agencies have recognized the significance of the crime scene and employ specially and extensively trained personnel to process them.
• The processing of a crime scene is a method of “careful destruction”: It is a one-way street, and one can never go back and undo an action.
• Standard operating procedures and protocols guide the crime scene investigator (CSI), providing a framework for comprehensive and accurate evidence collection, documentation, and transmittal to the laboratory.

Of Artifacts and Evidence

• The goal of an archaeological excavation is to carefully collect and record all the available information about a prehistoric or historic site of human activity.
• The goal of processing a crime scene is to collect and preserve evidence for later analysis and reporting.
• These processes have in common is that they are one-way: Once an action is taken, an artifact moved, a piece of evidence collected, it can’t be undone any more than a bell can be “un-rung.”
• Crime scenes and archaeological sites are made up of the physical remains of past human activity and, in a sense, are snapshots of the “leftovers” of a completed process.
• When a scene is processed or a site dug, the procedure is one of “careful destruction”: The scene or site will never exist in exactly the same way as it did before the process started.
• All the information, the relationships, the context of the items must be documented as they are destroyed to allow for some level of reconstruction in the laboratory or museum.
• It is an awesome responsibility to work a scene or excavate a site, and neither should be taken lightly.
• The first technical term is a datum, a fixed reference point for all three-dimensional measurements.
• An artifact is a human-made or modified portable object.
• A feature is a non-portable artifact, such as a fire pit, a house, or a garden.
• Organic or environmental remains (non-artifactual) are natural remnants that nonetheless indicate human activity, such as animal bones or plant remains but also soils and sediments.
• An archaeological site, then, can be thought of as a place where artifacts, features, and organic remains are found together. Their location in relation to each other sets the internal context of the site.
• The term provenance is the origin and derivation of an item in three-dimensional space, in relation to a datum and other items.
• Evidence can be defined as information, whether personal testimony, documents, or material objects, that is given in a legal investigation to make a fact or proposition more or less likely.
• Most of the evidence relates to physical evidence—that is, things involved in the commission of the crime under investigation.

Crime Scene Investigation

• Each crime scene is unique.
• Although nearly every police and forensic agency has written protocols about processing a crime scene, these may be trumped by the circumstances of the crime scene.
• Situations demand that investigators be flexible and creative when necessary.

First on the Scene

• The success of any crime scene investigation depends in large part on the actions taken in the first few minutes after the First Officer (or FO) or CSI arrives.
• Crime scenes are a complex mix of static and dynamic information, a scene fixed in time like a photograph but slowly degrading, much like poorly archived historical photographs.
• The majority of the physical evidence will be generated by the processing of the crime scene, and the relationships between the people, places, and things (the context) will tell the story of what happened.
• The primary task of the FO at a crime scene is to secure the scene and prevent destruction or alteration of the critical and sometimes fragile context of a crime scene.
• The assumption is that the perpetrator has left physical evidence at the crime scene.
• Therefore, the FO’s duties are simple in concept but complex in execution:
  1. Detain any potential suspects.
  2. Render medical assistance to those who need it.
  3. Do not destroy, alter, or add any evidence at the scene.
  4. Prevent others, even superiors, from doing the same.
• The FO should not simply rush into a scene but approach it carefully, thoughtfully.
• Sometimes the best thing to do is just prevent further entry until additional agency staff arrive.
• Once the immediate scene is secured, the lead investigator further defines and evaluates the scene.
• With the crime scene defined and its borders identified, the initial surveyor begins to develop an overview and devise a plan of action.

Plan of Action

Preparation

• The officers or investigators assigned to the scene should have obtained a search warrant, if necessary, by the time the crime scene processing begins.
• If there is time, the search should be discussed with involved personnel before arriving at the scene.
• A command station for communication and decision-making should be established in an area away from the scene but still within the secured perimeter.
• Personnel task assignments should be made before arrival at the scene.
• Communication between the various agencies’ representatives, such as medical examiners, laboratory personnel, emergency medical technicians, and attorneys, is crucial to a smooth and successfully executed crime scene process.
• Think ahead. Fifteen minutes of thought can save hours, and possibly lives, later on.
• Prepare the paperwork to document the search before searching.
• Agree-upon terminology—if everyone refers to an area as the “living room,” then there will be less confusion afterward if questions come up
• Arrange for protective clothing, communication, lighting, shelter, transportation, equipment, food, water, medical assistance, and security for personnel.
• Processing crime scenes can be tedious, physically demanding work, and people, even professionals, perform poorly when they are tired.
• In prolonged searches, use multiple shifts or teams.
• If one doesn’t exist, develop a transfer mechanism for paperwork and responsibility from one team to the next.

Secure the Scene, Secure the Item

• If the FO hasn’t done so, take control of the scene immediately.
• Determine the extent to which the scene has, or has not, been protected.
• Talk to personnel who have knowledge of the original condition.
• Keep out unauthorized personnel.
• Record who enters and leaves, even if they are an agency’s superiors.
• Take too many notes. Regarding note taking.
• Central nature of crime scene notes includes documentation of who did what and when, contemporaneous with those activities.

Preliminary Survey

• The survey is an organizational stage to plan for the search.
• Cautiously walk the scene; professionalism and calm are called for.
• Take preliminary photographs to establish the scene and delineate the extent of the search area.
• Make note of special "problem" areas, such as tight spaces, complex evidence arrangements, or environments with transient physical evidence.
• Take extensive notes to document the scene, physical and environmental conditions, and personnel tasks and activities.
• Evaluate what physical evidence collection requirements there may be.
• Make sure enough supplies are available: running out of packaging or gloves halfway through is no good!
• Focus first on evidence that could be lost or damaged; leave the more robust evidence for last.
• All personnel should consider the variety of possible evidence, not just evidence within their specialties.
• Collection of evidence is more than just “bagging and tagging.”
• The easily accessible areas, of course, are processed first, but then move on to out-of-the-way locations, like in cupboards, under rugs or carpeting, or in drawers.
• Look for hidden items, secret compartments, and false fronts. Things may not be what they seem, and crime scene personnel must evaluate whether evidence appears to have been moved or altered.
• Remember, things at a crime scene are just things until they are designated as evidence and then recorded and collected.

Photography

• The photography of the crime scene should begin as soon as possible.
• The photographic log documents all the photographs taken and a description and location of what’s in the photograph.
• A progression of establishing (overall or perspective views), medium (within 6 ft), and close-up (within 12 in) views of the crime scene should be collected.
• Multiple views, such as eye level, top, side, and bottom, help to represent what the scene or a piece of evidence looked like in place.
• Start with the most fragile areas of the crime scene first; move through the scene as evidence is collected and processing continues.
• Document the process itself, including stages of the crime scene investigation, discoveries, and procedures.
• Photographs must at least be taken before the evidence is recovered.
• Photographs should be taken with and without a scale.
• Photographs that include a scale should also have the photographer’s initials and the date.
• Scales allow photographs to be reproduced at defined scales (1:1, 1:2, 1:10, etc.).
• Photograph the crime scene in an overlapping series using a wide-angle lens, if possible; 50 mm lenses are the standard issue for cameras—use both and lots of film.
• It’s almost impossible to take too many photographs.
• All these images can help later with reconstruction questions.
• When the exterior crime scene is photographed, establish the location of the scene by a series of overall photographs, including one or more landmarks, with 360° of coverage.
• Photograph entrances and exits.
• Prior photographs, blueprints, or maps of the scene may be of assistance, and they should be obtained, if available.

Sketch

• Crime scene sketches may look crude at times, but they contain one very important element for reconstruction: numbers.
• Sketches complement photographs and vice versa.
• Items of evidence can be located on the sketch as it is made to help establish locations later.
• Although sketches are quantitative, they are normally not drawn to scale.
• A sketch should include the following:
  • The case identifier
  • Date, time, and location
  • Weather and lighting conditions
  • Identity and assignments of personnel
  • Dimensions of rooms, furniture, doors, and windows
  • Distances between objects, persons, bodies, entrances, and exits
  • An arrow pointing toward magnetic north

Chain of Custody

• Arguably, the single most important piece of paper generated at a crime scene is the chain of custody.
• This form documents the movement of evidence from the time it is obtained to the time it is presented in court.
• The most compelling evidence in the world can be rendered useless if inaccuracies or gaps exist in a chain of custody.

Crime Scene Search and Evidence Collection

• The crime scene search should be methodical and performed in a specific pattern.
• The choice of pattern may be dictated by the location, size, or conditions of the scene.
• Typical patterns are spiral, strip or lane, and grid.
• Adhering to the selected pattern prevents “bagging and tagging” random items with no organization or system.
• Measurements showing the location of evidence should be taken with each object located by two or more measurements from non-movable items, such as doors or walls.
• These measurements should be taken from perpendicular angles to each other to allow for triangulation.
• Be alert for all evidence: The perpetrator had to enter or exit the scene!
• Mark evidence locations on the sketch and complete the evidence log with notations for each item of evidence.
• If possible, having one person serving as evidence custodian makes collection more regular, organized, and orderly.
• Again, if possible, two persons should observe evidence in place, during recovery, and being marked for identification.
• Use tags, or if feasible, mark directly on the evidence.
• Wear gloves to avoid leaving fingerprints
• Evidence should not be handled excessively after recovery.
• Seal all evidence packages with tamper- evident tape at the crime scene.
• An important activity often overlooked is the collection of known standards from the scene, such as fiber samples from a known carpet or glass from a broken window.
• Monitor the paperwork, packaging, and other information throughout the process for typographic errors, clarity, and consistency.
• Simple geometry can help locate and reconstruct where things were in a sketch.
• Always take measurements from at least two locations.
• This will help with checking distances and triangulating “untaken” measurements later.
• In trigonometry and elementary geometry, triangulation is the process of finding a distance to a point by calculating the length of one side of a triangle, given measurements of angles and sides of the triangle formed by that point and two other reference points.

Final Survey

• When the crime scene is finished, there is still work to be done!
• A final survey is recommended to review all aspects of the search.
• Discuss the search and ask questions of each other.
• Read over the paperwork for a final check for completeness.
• Take photographs of the scene showing the final condition.
• Secure all evidence and retrieve all equipment.
• A final walk-through with at least two people from different agencies (if possible) as a check on completeness is a must.
• The crime scene can be released after the final survey; this event should be documented in the paperwork, including the time and date of release, to whom and by whom it was released.
• Remember that other specialists, such as a bloodstain pattern analyst or medical examiner, may need access to the scene before it is released.
• Once the scene has been released, re-entry may require a warrant; therefore, the scene should be released only when all personnel are satisfied that the scene was searched correctly and completely.

Submission of Evidence to the Laboratory

• The collected evidence may be submitted to the laboratory by that agency’s personnel (that is, laboratory personnel) or by CSIs or law enforcement officers.
• A form is typically filled out or a letter written detailing what is submitted, under what criminal circumstances, who is submitting the items, and what laboratory examinations are requested.

Safety

• Walking into a crime scene is one of the most hazardous activities a forensic scientist or CSI can do.
• Chemical and biological threats abound, not to mention knives, firearms, explosives… the list goes on.
• Worse, coming in at or near the end of the action, crime scene personnel have little or no foreknowledge of what’s in store for them.
• Add in the prospect of intentional manufacture or use of chemical or biological agents or explosives by terrorists, and the issue of safety for crime scene personnel becomes of paramount concern.
• The increase in bloodborne pathogens (BBPs) (AIDS and hepatitis, for example) and other pathogens that may be encountered at crime scenes (like the Hantavirus) has made law enforcement and CSIs more aware of personal protection when responding to crime scenes.
• Although the risk of infection to crime scene responders is exceedingly low, precautions are typically mandated by individual agencies’ protocols.
• Additionally, federal laws or regulations from one of several health agencies may be applicable to crime scene personnel

Sources and Forms of Dangerous Materials

• Inhalation:
  • At a crime scene, airborne contaminants can occur as dust, aerosol, smoke, vapor, gas, or fume.
  • Immediate respiratory irritation or trauma might ensue when these contaminants are inhaled; some airborne contaminants can enter the bloodstream through the lungs and cause chronic damage to the liver, kidneys, central nervous system, heart, and other organs.
• Skin Contact:
  • Because processing a crime scene requires the physical collection of items, skin contact is a frequent route of contaminant entry into the body.
  • Direct effects can result in skin irritation or trauma at the point of contact, such as a rash, redness, swelling