Forensic Science Exam 1

Forensic Science

the application of sciences to Law

• the spectrum of the sciences is Enormous

Mathieu Orfila

father of forensic toxicology

• detection of poisons and their effects on animals

Alponse Bertillon

devised the first scientific system of personal identification, using body measurement = anthropometry

Francis Galton

conducted the first definitive study of fingerprints and their classification

• fingerprints

Leone Lattes

developed a procedure to determine blood type for dried bloodstains

• a, b, ab, o

calvin goddard

used a comparison microscope to determine if a bullet was fired from a specific gun

• tool marks on bullets

albert osborn

developed the fundamental principles of document examination

Hans gross

wrote the first treatise describing the application of scientific principles to the field of criminal investigation

edmond locard

contamination/physical evidence

• exchange principle-basis for transfer of evidence

• whenever two objects come into contact with one another and their is exchange of material between them

alexander gettler

first forensic chemist to be employed in the US/New York City

• Father of forensic toxicology

Crime Labs

LA police department

FBI

NC State bureau of investigation

Wake city-county bureau of identification

Major Federal Crime labs

FBI - Federal Bureau of Investigation

DEA - Drug Enforcement Administration

ATF - Alcohol, tobacco, Firearms, Explosives

US postal inspection service

Crime Lab Units

• Standard

  • Physical science 

  • Biology 

  • Firearms 

  • Documents 

  • Photography  

• Optional 

  • Toxicology 

  • Fingerprints 

  • Polygraph

  • Voice Print

Two Types of Evidence

• Testimonial evidence

• Physical evidence  

Testimonial evidence

•  Is given in the form of a statement under oath in response to questioning 

physical evidence

• Is anything used, left, removed, altered or contaminated during the commission of the crime, by either the victim(s) or suspect(s)

• Cannot lie, forget, be mistaken when properly identified, collected, and preserved 

• Is demonstrable 

• Is not dependent on the presence of witnesses

• Is, in some instances, the only way to establish the elements of the crime 

• Physical evidence integrity comes from strict guidelines htat insure careful and systematic collection, organization and analysis of information known as the “scientific method” 

• CSI

  • physical evidence is connected to: the suspect, the victim, the object, the crime scene

Individual characteristics 1

• A piece of evidence that is unique and can be identified to the exclusion of all others

• Fingerprints 

• DNA  

Class characteristics 1

• Features shared by all members of a group or class 

• Footprints 

Expert Testimony

• Expert testimony can be a factor in determining a person’s guilt or innocence. The forensic scientist may be required to testify about their methods, results, and conclusions at the trial 

• Trial court judges have broad discretion in accepting an expert witness’s testimony

• An expert witness may be questioned about their ability and competence pertaining to the matter at hand 

• Education, membership in professional organizations, published books and articles, and years of experience are all determining factors on admissibility of an expert’s testimony

Forensic Scientists and the CSI

• The work of the forensic scientist has little value is the evidence has not been identified, recorded, collected, and preserved at the scene of the crime 

• It is the responsibility of the forensic scientist to train and educate law enforcement in the identification, recording, collection, and preservation of the physical evidence

• This relationship between the forensic scientist and the crime scene investigator is very important 

Crime Scene Investigation objectives

• Location according to criminal activity

  • Primary vs. secondary  

• Size 

  • Macro vs. micro

• Type

  • Homicide, robbery

•  condition

  • organized  vs. disorganized 

  • Planned vs. unplanned 

• Physical location 

  • Indoors, outdoors, vehicle

• Associated criminal behavior 

  • Passive vs. active 

Crime scene models

• Traditional 

  • Uses patrol officers and detectives as crime scene technicians 

  • Useful if resources and demand are relatively low 

  • Minimal experience and time commitment conflict with regular duties 

• Crime scene technicians 

  • Specially trained, full-time civilian personnel 

  • Continuity, specialization, scientific/technical training

  • Minimal investigative experience; lack global view of investigation

• Major crime scene squad 

  • Full-time, sworn officers 

  • Primary assignment: increased experience 

• Lab crime scene scientist 

• Collaborative team 

Multilevel crime scene security

• Level 1: overall scene security for restriction of general public 

  • Media 

• Level 2: restriction to official business

  • Command center  

• Level 3: target area (highest security) 

Documentation and Photography 

• Most important and time-consuming activity at the scene 

• Purpose: permanently record the condition of the crime scene and its physical evidence 

  • Crime scenes are transitory and immediately begin to change

• Skills needed: problem-solving, innovation, and originality 

5 Elements of an Investigative Report

completeness

• Covers all details concerned with the incident and all facts known to the officer 

• Uses full and complete sentences with no jargon 

• Notes what information is lacking or incomplete and what efforts may be made to obtain the information

Conciseness 

• A concise report is not simply brief but it makes every sentence count without being superfluous 

• Clearness

  • The report writer should use words that directly describe the event rather than the writer's response to the situation

  • Do not use words that can be interpreted in different ways by different groups; no judgments or conclusions

Correctness 

• This is the overall objective of the report and is best achieved by limiting the data in the report to sensory observations: sight, hearing, and touch. This reflects the integrity of the reporting officer 

• Courteous and Fair 

  • Provides an unbiased and objective reporting of the data and facts and is not subjective

Body Fluids

Blood, semen, urine, and saliva

ALS (alternate light source) is useful in locating such evidence

Fibers

• Natural and synthetic fibers that are transferred between victim and suspect are useful in establishing a link between the two

• Key is for the CSI to know and when to collect them 

• An Alternate Light Source (ALS) is helpful in locating fibers

class characteristics 2

• Not all evidence possesses individual characteristics that will allow an examiner to determine it is unique 

• When evidence only possesses class characteristics it is associated with a group not a single source 

• A new car has paint like many other new cars on the lot but if it is repainted after an accident it is now in a smaller group. It becomes more unique 

individual characteristics 2

• Evidence that is associated with a common source is said to process individual characteristics

• Fingerprints, bullets, tool marks, footwear impressions 

• The more individual characteristics, the higher the probability for a match

• Mathematical exactness is becoming more important 

  • Shoes size and patterns is a comparison 

  • Examiner can compare points identification and make an identification 

AFIS

• Automatic Fingerprint Identification System

  • AFIS is a statewide database of fingerprint information

  • IAFIS - Integrated AFIS 

  • To search IAFIS print must be of suitable quality 

  • Latent fingerprint points are marked and submitted for search 

  • Comparisons

DNA Databases

• CODIS - Combined DNA Index System 

  • Maintained by FBI 

• All 50 states have agreed to establish data banks of DNA profiles of convicted sex offenders and other crimes dependent on state laws 

• Maryland v. King 

  • Arrested suspects supported by probable cause for serious offenses DNA sample is like fingerprinting and photographing 

NIBIN & IBIS

• NIBIN 

  • National Integrated Ballistics Information Network

  • Integrated Ballistic Identification System 

• IBIS

• Maintained by BATF

• Allows firearms examiners to compare markings on bullets and shell casings recovered from crime scenes

• IBIS works like AFIS in this it gives examiners possible candidates to compare 

what is blood pattern analysis

• It is the “what” of bloodshed and can help reconstruct a scene 

  • Direction of travel of the blood droplets 

  • Distance of blood source to target surface 

  • Angel of impact of the blood droplet

  • Determination of blood trails 

  • Nature of the object to cause the bloodshed 

  • Interpretation of contact or transfer patterns 

Effects of surface texture

• Surface texture and the stain’s shape, size, and location must be considered when determining a bloodstain’s direction, dropping distance, and angle of impact 

• Surface texture is of paramount importance

  • In general, the harder and less porous the surface, the less spatter results 

  • Effects of surface texture on bloodstain from a single drop falling from 36’

  • Production of spines and small spatters around the periphery of the central bloodstain as a result of contact with rough textures 

• Drop volume as a function of source

  • Increased surface area of the source object results in a larger volume with larger drops 

Directionality

• The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion

  • 90 degree angle - perfect circle 

  • 20 degree angle - oval with blood droplet 

Impact of bloodstain spatter patterns

• Impact Spatter occurs when an object impact a source of blood 

• Forward spatter is projected outward and away from the source 

• Back spatter also known as blow-back spatter is projected backward from the source 

• If the bullet does not exit the body, a gunshot produces only back spatter

Determining the angle of impact

• Sin A = width of bloodstain/length of bloodstain 

• Sin of the equation = the angle/degree of impact

Classifying impact spatter

• Low velocity spatter 

  • Drops with diameters of 4mm or more normally produced by an applied force of up to 5ft/sec

• Medium velocity spatter

  • Drops with diameters from 1-4 mm with an applied force of 5 to 25 ft/sec

• High velocity spatter 

  • Drops with diameters of less than 1 mm from an applied force of 100 ft/sec or faster

expired bloodstain patterns

Expired Bloodstain Patterns 

• Forcefully expelled blood from the nose or mouth that has accumulated in the lungs, sinuses, and airway passages of the victim as a result of trauma 

• Similar to those of impact spatter from beatings or gunshots 

• Specific features: 

  • Vacuoles - ruptured air bubbles 

  • Dilution from saliva or nasal secretions