The Role of Forensic Laboratory

Forensic or crime laboratories are places where physical evidence from crime scenes, victims, and suspects is looked at. When preparing for a court case or trial, the lab's scientific results are used along with those from other areas of forensic science and criminal investigation.

Defining the element of the crime

This serves as evidence that a crime has been committed, such as when drugs or other controlled substances are identified and measured or when the blood alcohol content of someone accused of drunk driving is determined.

Providing investigative leads for a case

An example of this would be determining a car type in a hit-and-run case using automotive paint and glass studies.

Linking a crime scene or a victim to a suspect

This connection could be established by analyzing numerous types of physical evidence, including hair, blood, sperm, and fingerprints.

Corroborating or refuting a suspect’s statement or alibi

In a fatal gunshot case, bloodstain patterns at the scene and on a suspect's clothing may show whether a victim was fighting an assailant or in a different position when the shot was fired. Physical evidence can separate homicide from suicide. Physical evidence can answer issues like, "Did the victim fire the fatal shot?" or "Did the victim generate those bloodstains?"

Identifying a suspect

Fingerprint comparison or DNA profiling are not the only ways to find out who a suspect is, but they are often used.

Inducing a confession of a suspect

If a suspect is shown facts that have been proven by testing physical evidence, such as the victim's blood on their clothes or fingerprints on a weapon, they may be more likely to admit to committing a crime.

Exonerating the innocent

There may be physical evidence that proves a person did not commit a crime. This is commonly known as exculpatory evidence. An example of this form of evidence would be the absence of the suspect's DNA in vaginal samples of a rape victim's seminal fluid.

Providing expert testimony in court

The expert's presentation of physical evidence in court is the ultimate test of the evidence's validity. The expert's conclusions must meet stringent scientific proof criteria and withstand a tough cross examination by defense counsel at trial. To aid juries in reaching a proper decision in a case, physical evidence and scientific conclusions must be communicated in a comprehensible manner.

Types of Physical Evidence

Depending on the circumstances surrounding the illegal occurrence, physical evidence may exist in almost any shape or size. Depending on the actions of the parties involved, it may be present at the crime scene, or it may have been transmitted between the victim and the attacker, as well as to any other area. The forensic scientist must physically or chemically identify materials to the highest level of scientific certainty feasible using the available equipment as part of their investigation and analysis of physical evidence.

Body fluids

Usually seen on clothing or other materials or items, blood, semen, or saliva in liquid or dry form.

Body tissues

For toxicological investigation, several organ samples were taken at the autopsy along with blood, urine, and stomach contents.

Drugs and controlled substances

Plant parts, powders, tablets, capsules, or other forms that can be used to identify and weight.

Fibers

natural fibers (like cotton and wool) or man-made fibers (like rayon and dacron) to identify and compare.

Finger, palm, and foot prints

For identification and comparison, visible or latent prints are lifted or cast from different surfaces. In this category, you'll often find tire and shoe impressions.

Fire and explosive materials

Identification of accelerants and explosive residues using liquids, solid substance, or charred debris.

Firearms and projectiles

firearms and ammunition to determine the kind and origin of projectiles, measure distances, and ensure that firearms are functional.

Glass

Large sections Glass fragments may be linked to a suspect and a break-in, or they may show force direction or round sequence. Auto accident reconstruction uses glass analysis.

Hair

To ascertain species, race, and body part origin from a crime scene, victim, or suspect. Human hair can identify a suspect. Crushed, cut, burned, violently removed, or spontaneously lost hair can also be detected.

Oils and grease or cosmetic products

Transferred between items and individuals, each with their own makeup for comparison.

Paint and paint products

In a car accident, on many surfaces that may have been transported. Vehicle-hit pedestrians' clothes are evaluated for paint fragment transfer.

Serial numbers

Frequently changed or removed from cars, guns, and other items, but can be restored for accurate identification using chemical etching.

Soils and minerals, wood, and other vegetation

Identified and compared with possible sources or locations that may be associated with a suspect or victim.

Tool marks

Surface marks that may reveal the thing that generated them. The impression may be compared to wear features on a prybar or screw driver.

Questioned documents

Handwritten, typed, copied, or computer-generated materials that are evaluated for indications of forgeries are examples of physical evidence. To determine authenticity, exams may include ink and paper analyses as well as handwriting comparison. In the case of erased, physically damaged, or burnt papers or materials, restorative processes may be used.