Forensics Chapter 1 & 2

Forensic Science- is the application of science to criminal and civil laws.


  • Forensic science owes its origins to individuals such as Bertillon, Galton, Lattes, Goddard, Osborn, and Locard, who developed the principles and techniques needed to identify or compare physical evidence.


  • Mathieu Orfila

    • The Father of forensic toxicology


  • Alphonse Bertillion

    • Identify an individual 


  • Franics Galton

    • Conducted the first definitive study of fingerprints and their classification


  • Leone Lattes

    • Developed a producer to determine blood type from died bloodstains


  • Calvin Goddard 

    • Used a comparison microscope to determine if a particular gun fired a bullet 


  • Albert Osborn 

    • Developed the fundamental principles of document examination.


  • Walter McCrone

    • Utilized microscopy and other analytical methodologies to examine evidence


  • Hans Gross

    • Wrote the first treatise describing the application


  • Edmond Locard 

    • Incorporated Gross principles within a workable crime laboratory 


  • Locard’s Exchange Principle 

    • States that when a criminal comes in contact with an object or person, a cross-transfer of evidence occurs. 

The Crime Lab


  • The ever increasing number of crime laboratories is partly the result of the following:

    • Supreme Court decision in the 1960s responsible for police placing greater emphasis 

    • Crime lab is inundated with drug specimens due to accelerated drug abuse.

    • The advent of DNA profiling 


  • The development of crime labs in the U.S has been characterized by rapid growth accompanied by a lack of national and regional planning and coordination.

  • At present, approximately 411 crime labs operate at various levels of government-federal, state, county, and municipal.


Technical Support 


  • The technical support provided by crime labs can be assigned to five basic services. 

    • Physical Science Unit incorporates the principles

    • Biology unit applies the knowledge of biological sciences in order to investigate blood fluids, hair and fiber samples 

    • Photographic Unit applies specialized photographic techniques for recording and examining physical evidence. Some crime labs may offer a number of optional services 

    • Voiceprint Analysis Unit attempts to tie a recorded voice to a particular suspects. 

    • Evidence- Collection Unit dispatches specially trained 


The Scientific Method:


  • Formulate a question worthy of investigation 

  • Formulate a reasonable hypothesis to answer the question 

  • Test the hypothesis through experimentation 

  • Upon validation of the hypothesis


A forensic scientist must be skilled in applying the principles and techniques of the physical and natural sciences to the analysis of the many types of evidence that may be recovered during a criminal investigation 


  • A forensic scientist may also provide expert court testimony 

  • An expert witness is an individual whom the court determines possess knowledge relevant to the trial that is not expected of the average person 


Skills of a Forensic Scientist 


  • The expert witness is called on to evaluate evidence based on specialized training and experience that the court lacks the expertise to do.

  • The expert will then express an opinion as to the significance of the findings 


  • The necessity for the forensic scientist to appear in  court has been imposed on the criminal justice system by the case of Mendez-Diazv. Massachusetts. 

The Frye Standard 


  • The Frye v. United states decision set guidelines for determining the admissibility of scientific evidence into the courtroom 


  • To meet the Frye standard, the evidence in  question  must be “generally accepted” by the scientific community.


  • However, in the 1993 case of Daubert v Merrell Dow Pharmaceutical, INC, the U.S Supreme Court asserted that the Frye standard is not an absolute prerequisite to the admissibility of scientific evidence. 


  • Trial judges were said to be ultimately responsible as “gatekeepers” for the admissibility and validity of scientific evidence presented in their courts, as well as all expert testimony.


The Daubert Criteria 


  • In Daubert, the supreme Court offered some guidelines as to how a judge can gauge scientific evidence:

    • Whether the scientific technique or theory can be( and has been) Tested. 

    • Whether the technique or theory has been subject to peer review and publication.

    • The technique potential rate of error. 


  • In Daubert, the supreme court offered some guidelines as to how a judge can gauge scientific evidence:

    • Exientinc and maintenance of standards controlling 


Special Forensic Science Services 


  • Forensic Psychiatry is an area in which the relationship between human behaviour and legal proceedings is examined.


  • Forensic Odontology- involves using teeth to provide information about the identification of victims when  a body is left in an unrecognizable state; also investigations bite marks.


  • Forensic Engineering is concerned with failure analysis, accident reconstruction , and causes and origins of fires or explosions.


  • Forensic Computer Science involves the examination of digital evidence 


Monday February 3rd 2025 

Chapter 2


Arrival at the Crime Scene 


  • Upon arrival at a crime scene the first responding police officer to a crime scene is responsible for: 

    • 1. Acquiring medical assistance for injured victims 

    • Medical personnel avoid disturbing evidence and approach the victim by an indirect route 

    • 2.Detaining any potential suspects or witnesses 

    • Statements are taken from victims, witnesses and suspects

    • 3. Securing the crime scene to the greatest extent possible 

    • 4. Calling for any additional personnel needs such as other officers and or forensic investigators 


Securing the Crime Scene 


  • The boundaries of the crime scene must be secured with crime scene tape, ropes or cones. 

  • Investigators should never do anything that might alter the crime scene including smoking, eating, drinking.

  • The search for physical evidence at a crime scene must be thorough and systematic. The search pattern selected will normally depend on the size and locale of the scene and the number of collectors participating in the search 

  • For a factual, unbiased reconstruction of the crime, the investigator, relying upon his or her training and experience, must not overlook any pertinent evidence.

  • Physical evidence can be anything from massive objects to microscope traces 


Recording methods


  • Photography, sketches, and notes are the three methods for crime-n scene recording

  • Ideally all three should be employed; however, as is often the case, personnel and monetary limitations may prohibit the utilization of photography at every crime site.


Crime scene notes 


  • Note taking begins when the investigator is contacted and requested to report to the crime scene

  • The crime scene notes should begin with:

    • The identify of person who contacted the investigators 

    • Time of contact and arrival at the crime scene 

    • Preliminary case information 

    • Personnel present on arrival and those being contacted 


  • Notes contain a personnel log, all observations made by the investigator, and the time observations were made.

  • Notes are taken in a uniform layout, concurrently as the observations are made.

  • Notes are written in a bound notebook in blue or black ink.


Digital Photography


  • The number of pixels is directly related to the resolution of the picture. Photographs with more pixels show increasingly good resolution, or more detail and sharpness in photography.

  • The number of pixels that a camera features is usually measured in millions of pixels, or megapixels 


Crime scene photographs 

  • Each crime scene should be photographed as completely as possible in a logical succession. The sequence will show the overall scene first, then work down to individual pieces of evidence that jurors in the trial can easily relate back to the overall scene

  • The four minimum photographs required at a crime scene are an overview photograph, a medium range photograph, a close up photograph and a close-up photograph with a scale. 

  • Overview photos of the entire scene and surrounding area, including points of exit and entry, are taken first.

    • Taken from the outside borders of the scene and from various angles 

    • If the crime scene includes a body, photos must show the body’s position and location relative to the entire scene

    • Include a “visual tag”, an object recorded in multiple overview photos, to help visually piece the scene together 


  • Medium- range photos show the layout of smaller significant areas of the crime scene. 

    • Taken with evidence markers in place show the spatial relationships 

    • Include at least on photo of the “center” of the scene 


  • Close- ups photos are taken last and show greater detail of individual objects or evidence 

    • Taken at a 90 angle to the object with and without evidence markers and scales.

    • Scales shouldn’t be placed as close to the evidence as possible without affecting it in any way

    • After the 90 photos have been taken, photos from the other angles may be taken 

    • The most important close up photos are those depicting 

    • After the body is removed from the scene, the surface beneath the body should be photographed.


  • The walkthrough-initial survey of the crime scene

  1. Perpetrator's point of entry and exit are located 

  2. Indirect path is taken to the center of the crime scene 

  3. Obvious items of evidence are located


Procedures for collection


  • Often, many items of evidence are clearly visible but others may be detected only through examination at the crime laboratory.

  • For this reason, it is important to collect possible carriers of trace evidence, such as clothing, vacuum sweepings, and fingernails scarpings, in addition  to more discernible items 

  • Investigators handle and process physical evidence in a way that prevents changes to the evidence through contamination, breakage, evaporation, accidental scratching or bending, or through improper or carless packaging   

  • The use of latex gloves, disposable forceps, and sanitized equipment

  • Each different item or similar items collected at different locations must be placed in separate containers. Packaging evidence separately prevents damage through contact 


  • If biological or bloodstained materials are stored in airtight containers, the accumulation of moisture may encourage the growth of mold, which can destroy the evidential value. 


Chain of Custody 

  • A list of all persons who came into possession of an item evidence  


Obtaining Reference Samples


  • Standard/ Reference Sample 

    • Physical evidence whose origin is known, such as blood or hair from a suspect, can be compared to crime scene evidence.


  • The examination of evidence, weather it is soil, blood, glass hair fibers

  • 4th Amendment- search and seizure