Introduction to Forensic Science: History, Crime Scene, Evidence Collection

Forensic Science

the application of scientific techniques to the criminal justice system.$Yi Yu Ji

Forensic Science

the application of scientific techniques to the criminal justice system.

Yi Yu Ji

among the first to recognize that fingerprints are a means of identification.

Toxicological Evidence at Trial

First used in 1839 - Detection of arsenic in the victim's body - James.

Alphonse Bertillon

Father of Criminal Identification (1879).

Francis Henry Galton

Identification by Fingerprints (1872).

Edmond Locard

First Crime Lab & Locard's exchange principle (1910).

Locard's exchange principle

When 2 objects come into contact with each other → an exchange of materials.

Orflia

Father of Forensic Toxicology.

Bertillion

father of Criminal identification (Anthropometry).

Lattes

testing bloodstains for blood group identification.

Obsorn

examining documents & using them as scientific evidence.

Goddard

use of microscopy for fireman examination.

Jefferys

First DNA Profiling.

LA Police Department

The oldest crime lab (1923) - Created by August Volimer.

U.S. crime labs

The U.S. now has around 400 crime labs with varying levels and services.

Three Main Functions of Crime Labs

Analyze physical evidence, Providing Expert Testimony, Preservation of Evidence.

Physical evidence

the only evidence that is free of bias.

Eye-witness testimony

Have more potential to be inaccurate.

Scientific Method

Guidelines for collection, organization, and analysis of evidence.

Hypothesis

A proposed explanation made on the basis of limited evidence as a starting point for further investigation.

Frye Standard

A standard that became problematic for new techniques because they didn't have the chance to earn 'general acceptance.'

The Federal Rules

Expert testimony is admissible if the expert has knowledge, skill, training, or education.

Admissible evidence

Evidence that meets specific criteria to be considered in court.

Expert witness

A forensic scientist who may have to defend scientific contributions to the case in the courtroom.

Recognition, Collection, & Preservation of Evidence

Forensic scientists cannot effectively do their jobs if crime scene evidence is not properly recognized, collected, and preserved.

Probability Timer

100% probability of solving the crime right after the crime occurs.

Crime scene changes

The probability of solving the case decreases as the crime scene changes.

First Step - Secure the Crime Scene

The first responding officer has the responsibility to preserve and protect the area as much as possible.

Second Step - Isolate the Crime Scene

Remove everyone except people who need medical assistance and rope off areas where evidence may have been discarded.

Third Step - Detain All Involved Parties

Detain witnesses, people involved, and suspects for questioning.

Witness accounts

Eyewitnesses are aware and present when the crime happened and can provide details.

Crime scene preservation

To keep the crime scene from changing, video, picture, or audio recording is necessary.

Collect Physical Evidence

Collect evidence from the time of the crime and properly store and maintain it.

Medical assistance

Obtain medical assistance as part of securing the crime scene.

Guarding the crime scene

Position a guard to keep untrained personnel and press out of the crime scene.

Lead Investigator

The person responsible for overseeing the crime scene and ensuring proper procedures are followed.

Initial Walkthrough

The process where the Lead Investigator moves through the entire crime scene before any sketches, photographs, or searches are conducted.

Handwritten Notes

Notes taken by hand that convey stronger authenticity and do not require batteries.

Audio Notes

Notes recorded in audio format that allow for hands-free observation but may be difficult to understand if muffled.

Video Notes

Visual recordings of the crime scene that can be shown in court but may distract from actual observations.

Common Approach Path

The best way to survey the crime scene and collect evidence without disturbing it.

Homicide

The deliberate and unlawful killing of one person by another; murder.

Burglary

Entry into a building illegally with the intent to commit a crime, especially theft.

Crime Scene Boundaries

The defined limits of the crime scene that must be established to secure the area.

Systematic Searches

Organized methods of searching that minimize the chance of missing crucial evidence.

Evidence Collection

The process of gathering physical items that can be used to support or refute a hypothesis about a crime.

Murder Weapon

The object used to commit homicide.

Blood, DNA

Biological evidence that can link a suspect to a crime scene.

Pros of Handwritten Notes

Notes won't break or run out of batteries and cannot be accidentally deleted.

Cons of Handwritten Notes

Doesn't leave hands free and detailed writing is time-consuming.

Pros of Audio Recordings

Allows hands-free recording and faster spoken observations.

Cons of Audio Recordings

Can be muffled, may forget to press 'Record', and can run out of battery.

Pros of Video Recordings

Provides visual context for the jury and allows for hands-free observation.

Cons of Video Recordings

Can distract from observations and may malfunction or run out of battery.

OJ Simpson Case

Criminally found not guilty of murder due to mishandled evidence; found guilty in a civil case and ordered to pay

35.5 million.

Crime Scene Processing Procedure

The established method for handling and analyzing evidence at a crime scene.

Hypothesize Likely Events

The process of making educated guesses about what occurred during the crime based on observations.

Hit and Run

motor accident in which the vehicle involved does not stop

Tool marks

forced entry

Fingerprints

unique patterns left by fingers

Shoe prints

imprints left by footwear

Footprints

imprints left by feet

DNA

genetic material used for identification

Hair

strands used for forensic analysis

Fibers

small strands used for forensic analysis

Tire Marks

imprints left by vehicle tires

Paint scrapings

small pieces of paint collected for analysis

Blood

biological fluid used for forensic analysis

Body tissue

biological material used for forensic analysis

Organizing the Search

speeds up the process of finding evidence and minimizes the possibility of missing evidence

Strip/Line Search pattern

investigators begin at one end of the search area and continue forward in the same direction, only needs 1-2 trained investigators, used for well-defined boundaries

Grid Search Pattern

two or more investigators overlapping separate line searches to form a grid, uses 2 or more trained investigators, good for looking for many small pieces of evidence

Spiral Search

only needs 1 trained investigator, used for not well-defined boundaries, good for searching smaller crime scenes with a centralized location of evidence

Wheel/Ray Search Pattern

investigators stand back to back at the center point and walk outwards in different directions, needs multiple trained investigators (at least 5), used for searching a large crime scene with a centralized location of evidence

Quadrant/Zone Search

scene is divided into sections, team splits up for each member to search a zone for evidence, needs multiple trained investigators, used for searching large crime scenes

After finding evidence

record it in notes, mark evidence with lettered/numbered evidence marker, inform Lead Investigator of evidence, DO NOT TOUCH EVIDENCE

Photography & Videography at the Crime Scene

closest way to preserve it, helps jurors of a trial see what the crime looked like, allows review of a crime scene

Photography Guidelines

take all photographs before touching or moving anything, photograph rooms from all angles, photograph all potential points of entry/exit from multiple angles

How to Take Crime Scene Photos

all evidence must have a numbered or lettered evidence marker with it, 1st picture - very wide shot from far away, 2nd picture - medium shot, 3rd picture - close up shot, 4th picture - close up shot with ruler (or any other scale)

Crime Scene Photos → Wide Shot

shows where the evidence is in relation to the entire crime scene

Crime Scene Photos → Medium and Wide Shots

shows where the evidence is related to specific area in the picture/crime scene

Crime Scene Photos → Close Shot

clear, detailed picture of the evidence, one shot taken without ruler or scale, second shot is taken with ruler or scale

Videotaping the Crime Scene

video includes wide, medium, and close-up shots with each piece of evidence

Why We Need a Crime Scene Sketch

blueprint of the crime scene, helps jurors understand the crime scene better, helps other detectives who are not present to understand the crime scene better

Rough Sketch

Sketch made at the crime scene that cannot be changed after the sketch artist has signed and left; it is not done to scale.

Finished Sketch

Official crime scene sketch usually made using digital software, done to scale, and primarily used in court.

Crime Scene Sketch Guidelines

Includes measuring everything, including every piece of evidence on the sketch, case specific info/title block, and indicating which direction is North.

CSI Bunny Suit

Protects the crime scene from contamination and protects the Evidence Technician.

Gloves

Should be changed after checking each piece of evidence.

Forceps

Use new forceps for each piece of evidence to avoid cross-contamination; clean and sanitize forceps.

Documentation Completion

No evidence should be moved until all documentation has been completed for that piece of evidence (notes, photograph).

Locard's Principle

All things that come in contact with each other leave a trace; all possible carriers of trace evidence must be examined.

Trace Evidence

Includes evidence apparent to the naked eye and requires examination of all clothing worn by anyone connected to the crime.

Collecting Evidence

Bodies at a crime scene should have their hands papered or cloth bagged and taped; do not remove trace evidence on clothes, weapons, etc.

Type of Evidence Packaging

Type of evidence dictates how to package the evidence: biological, non-biological, trace evidence, or burnt/charred.