Crime scene investigators collect evidence such as fingerprints, footprints, tire tracks, blood and other body fluids, hairs, fibers and fire debris.

Missing elements are the time, a description of type of crime, and measurements of the scene.

Physical evidence encompasses any and all objects that can establish that a crime has been committed or can link a crime an it’s victim or it’s perpetrator. Examples include hair, skin, fibers, fingerprints, blood, DNA, weapons, soil, glass, and documents.

Collecting prints at the crime scene should be every investigator’s top priority. Fingerprints from the suspect as well as elimination fingerprints from the victim will also be needed for comparison (the same holds true for palm and bare footprints).

Evidence handling is the process of how electronic evidence was handled from the moment of seizure to the presentation in a court of law. It covers admissibility, authenticity, complete, reliable, and believable.

At major crime scenes impressions should be photographed before they are casted. Photography is done first because casting the impression will destroy the original impression and eliminate the ability to photograph the impression afterward.

Toolmark evidence should be packaged to prevent damage or loss of trace evidence. On painted surfaces bearing a toolmark, sample scrapings of the paint should be collected from areas around the toolmark for submission to the Laboratory.

There are three major categories of tool marks: indentations marks, abrasion marks, and cutting marks.

Toolmarks

• Evidence submitted in toolmark cases may include tools such as: bolt cutters, screwdrivers, scissors, knives, pliers, crowbars, and saws.
• Toolmarks are scratches and/or impressions that are left on an object that is softer than the object or tool that caused the marks.

There are two main types of toolmarks that can be distinguished: slipped and molded impressions. The slipped impression occurs as the tool drags or slides across the surface.

Striated toolmarks (also called striae, friction marks, abrasion marks, or scratch marks) – produced when a tool is placed against another object and moved parallel to and across the object with pressure applied. The striations consist of the resulting surface contour variations.

The NIST Ballistics Toolmark Research Database is an open-access research database of bullet and cartridge case toolmark data. This database will: foster the development and validation of measurement methods, algorithms, metrics, and quantitative confidence limits for objective firearm identification.

(2) Individual Characteristics Marks produced by the random imperfections or irregularities of tool surfaces. These random imperfections or irregularities are produced incidental to manufacture and/or caused by use, corrosion, or damage. They are unique to that tool and distinguish it from all other tools.

In crime scene investigation, toolmarks found in the scene of crime should be photographed by the analyst in close range, mid range and overview range shots in order to record it’s original location, shape, size and number if multiple tool marks are present.

Tool-mark analyses help forensic scientists identify the tool or tools used at the scene of the crime and link the tool(s) to the criminal. Investigators compare marks by examining detailed photos or silicone casts of the marks and collect trace evidence (such as residue) left behind by the tool.

Nature of Evidence Tool marks are encountered most frequently in burglary cases but may also be found in other types of crimes. The evidence consists of striations or impressions left by tools on objects at the crime scene and various types of tools found in the possession of suspects.

“The best evidence is anything that can be linked to a unique, single, specific source. This is called individual evidence. Examples are fingerprints, handwriting, DNA patterns, and sometimes physical matches, such as a piece of broken glass that exactly fits to its mate (like a jigsaw puzzle piece).

Would this be considered class or individual evidence? Explain. This is class evidence because the ripped pieces cannot be matched to each other.

Footprints and tireprints As shoes and tires are used, individual characteristics such as nicks, cuts, and wear patterns develop. These characteristics may show up in prints and impressions and can be compared with a suspect’s shoes or tires.

Hair is considered class evidence when the follicle is not attached because the follicle is the part that contains DNA. When the follicle is attached, it is considered individual evidence.