Physical Evidence

Examples shown are possible evidence that may be found and collected at the crime scene, but are NOT all inclusive.

The only evidence that cannot be found is that which is not looked for.

Physical Evidence Any material that may aid in the determination of the truth during the investigation of a crime

Blood, semen and saliva ALL suspected blood, semen, or saliva – liquid or dried – animal or human Includes fluids dried onto fabrics or other objects Cigarette butts

These substances are subjected to serological and biochemical analysis for determination of identity, comparison and possible origin.

Documents ANY handwriting and typewriting submitted so that authenticity or source can be determined.

Related Document Items Paper Ink Indented writings – What do you think this means? Obliterations Burned or charred documents

Drugs Any substance seized in violation of laws regulating the: – sale – manufacture – distribution – use

Explosives Any device containing an explosive charge All objects removed from the scene of an explosion All objects that are suspected to contain the residues of an explosive

Fibers Any natural or synthetic fiber whose transfer may be useful in establishing a relationship between objects and/or persons.

Firearms and Ammunition Any firearm Discharged ammunition Intact ammunition

Glass Any glass particle or fragment Windowpanes containing holes or breaks

Hair Any animal or human hair present

Fingerprints All prints of this nature latent (hidden, undeveloped, or invisible) and visible.

Impressions Tire markings Shoe prints Depressions in soft soils All other forms of tracks Glove and other fabric impressions Bite marks

Organs and Physiological fluids Body organs and fluids are submitted for toxicology. Includes blood to be analyzed for alcohol or drugs.

Paint Any paint – Liquid or dried Look for that which may have been transferred from one object to another

Petroleum Products Examples: – Gasoline residue – Grease or oil stains

Plastic Bags Any disposable bags – Baggies (drug residue) – Garbage bags

Plastic, rubber and other polymers May be linked to objects recovered in possession of a suspect perpetrator.

Powder residues Items suspected of containing firearm discharge residues Items suspected to be associated with drugs.

Serial Numbers Includes all stolen property submitted to the laboratory for the restoration of erased identification numbers.

Soil and Minerals All items containing soil and/or minerals. – Could link a person or object to a particular location. Common examples: Soil imbedded in shoes Safe insulation found on clothes

Tool Marks Any object suspected of containing the impression of another object – Screwdriver or crowbar

Vehicle Lights Inspection is normally conducted to determine whether a light was on or off at the time of impact.

Wood and other Vegetative matter Fragments of wood, sawdust, shavings, or vegetative matter Found on clothing, shoes or tools – Could link a person or object to a location.

Significance of Physical Evidence Identification The process of determining a substance’s physical or chemical identity. Comparison The process of ascertaining whether two or more objects have a common origin

Similarities of hairs – Found on scene and compared with suspect Paint chip or paint scraping – Hit and run DO THEY COME FROM THE SAME SOURCE?

Classifying Evidence Direct Vs. Circumstantial Evidence Direct – Factual from eyewitnesses or confessions Circumstantial – Requires a judge or jury to decide – Comes from Forensic Science – Generally more Reliable than direct evidence

Forensic Evidence Individual: unique enough to narrow it down to one or a few suspects Class: only associates with a group IndividualClass

Evidence with Individual Characteristics is far better in court, but much harder to find than Class Evidence.

Forensic Evidence Physical: non-living – Fingerprints, shoe and tire impressions, tool marks, fibers, paint, glass, drugs, firearms, bullets and shell casings, documents, explosives, accelerants, etc. Biological: from living things – Blood, saliva, urine, semen, hair, plant material, animal or insect materials, etc. PhysicalBiological

Evidence DirectCircumstantial IndividualClass Physical Biological

Evidence Classification Example #1 A brown piece of hair is found on a victim. There is no follicle available for DNA recovery. The hair matches the characteristics of one of the suspects.

Evidence DirectCircumstantial IndividualClass Physical Biological

Evidence Classification Example #2 Skin is recovered from underneath a rape victim’s nails. DNA analysis matches the DNA of one of the suspects.

Evidence DirectCircumstantial IndividualClass Physical Biological

Evidence Classification Example #3 Bloody Sneaker Prints are recovered from the room where a victim of a gunshot wound is found. The sneaker prints contain several distinct cuts and wear marks that match cuts and wear marks on the suspect’s shoes.

Evidence DirectCircumstantial IndividualClass Physical Biological

Evidence Classification Example #4 A 37 year old Caucasian female is found, with a gunshot wound to the head, at the bottom of a lake next to a dock. A witness tells police that she saw the victim’s husband fire a gun into the side of the victim’s head at which point the victim fell into the lake.

Evidence DirectCircumstantial IndividualClass Physical Biological

Mathematical Probability The probability of any given occurrence at a specific place or time relates to the value of a piece of evidence. Ex) The likelihood of two different people sharing an exact print…

The less frequent the rate or probability of independent occurrences, the firmer the base of confidence becomes. The greater the frequency of an occurrence, the less significance that can be attached to its evidentiary value.

Crime-Scene Reconstruction Used to support a likely sequence of events by the observation and evaluation of physical evidence, as well as statements made by those involved with the incidence.

Important considerations in gathering evidence at a crime scene: Proper recognition of evidence Competent collection of materials Adequate preservation of samples Completion of the chain of custody

The successful outcome of a criminal investigation is almost directly related to the manner in which the evidence is collected and preserved The final evaluator of forensic evidence is the jury