The Florida Bar 1950
American Bar Association
Justia Lawyer Rating
Lake County Bar Associaton
Florida Justice Association

What are the Different Types of Scientific Evidence Used in Criminal Cases?

Scientific evidence, often referred to as "forensic" evidence, is widely used in the criminal justice system by prosecutors and defense attorneys alike. Whether in a case involving sexual assault, robbery, murder, or other offenses scientific evidence is often used at trial, although that doesn't mean it is always reliable. What are the different types of scientific evidence used in criminal cases not only in Florida but across the U.S.? We'll discuss some of them below.

Forensic evidence including fingerprint ID, DNA matching, and hair or fiber evidence is generally considered scientific evidence before jurors and judges who typically do not have the knowledge and experienced to understand methods used in the development of forensic evidence. In some instances, scientific evidence may even include ballistics, which pertains to guns or other firearms and the bullets fired from those weapons.

DNA analysis or evidence may include biological evidence taken from skin cells, bodily fluids, blood, or even hair. Because DNA or deoxyribonucleic acid is genetic material and differs between every individual who has a unique DNA profile, the results of these tests are said to be more than 99% accurate. The only instance in which more than one person may share a DNA profile is in the case of identical twins. DNA has helped many who have been wrongly convicted of a crime and incarcerated be exonerated and set free; in fact, hundreds have been proven not guilty through post-conviction DNA tests according to the Innocence Project.

Fingerprints have been used to identify people since ancient times, and are the most accurate although you may believe DNA would be the most reliable scientific evidence. Even in the case of identical twins, fingerprints are unique and identifiable by a trained expert. Fingerprints may be taken from a crime scene using powder or chemicals prior to lifting the print, or through ultraviolet lights if the fingerprint is latent. The unique ridges and points found with fingerprints make every individual's prints different.

Hair and fiber evidence. Experts can determine many things from a single hair including whether it is human, the race of the person, hair's color, chemical composition, presence of toxins, and more. For the most part hair evidence is used to exclude someone suspected of a crime, as the only way to know for absolute certain a hair found at a crime scene is the suspect's is if the root or follicle is attached, which can be DNA tested. For example, if the suspect is a Caucasian with brown curly hair and the hair in question is determined by experts to be that of an Hispanic person and is straight or black, it cannot be the hair of the suspect.

Fibers may originate from carpeting, fabric, upholstery, curtains, even clothing. Classified as either natural, synthetic, or manufactured, fibers are often useful to those investigating a crime scene due to the fact the origin of the fiber may be identified. A suspect may have a fiber from a victim's clothing on his or her own clothing, a carpet fiber on his or her shoe, etc.

Ballistics is considered scientific or forensic evidence by some, although many criminal defense attorneys consider it "junk science" as the reliability of the evidence can be in question. Ballistics are often used by investigators to determine the type of weapon used to commit a crime, the shooter's location based on the angle of trajectory of the bullet, the "rifling" of a spent bullet (marks made on the bullet while passing through the barrel) which can help determine the type of weapon used, and more.

Scientific evidence has proven extremely useful in criminal cases for both defense lawyers and prosecutors. However, it is important to keep in mind that errors can be made with any type of evidence. For instance, DNA evidence may be contaminated or compromised due to improper collection or handling. With every type of evidence whether forensic or circumstantial, there can be issues that leave questions in the mind of jurors. Even in criminal law cases, nothing is foolproof.

Client Reviews

I would like thank my attorney Thomas Luka. I knew from the beginning I had the right guy in my corner. While celebrating with family and friends at a Public Park in Seminole County, a fight broke out among various people. Myself, and a good friend, broke up the fight and the instigators left. Six months later, I was wrongly accused as the person who started the fight. The first attorney I hired could not even get a response from the State Attorney handling the case. Someone referred me to Tom and I felt comfortable at his demeanor and reactions.

After conversations with Tom, who knew I would settle for nothing less than a FULL DISMISSAL due to my innocence, I hired him. His firm of Adams and Luka did the due diligence by interviewing witnesses and the police who were on the scene, as well as starting a dialogue with the State Attorney. After gathering statements from witnesses, Tom was able to present a strong argument on my behalf to the State Attorney on why the case should be dismissed. If the State Attorney was not willing to dismiss the case, Tom was ready to take the case to trial.

The result by Thomas Luka: Case Dismissed.

I am 53 years old with a spotless record and glad to keep it that way thanks to the time, effort, hard work, and professionalism of the Adams and Luka and Tom Luka.

Earl from Mesquite
Thomas Luka left a life-long great impression of lawyers. He was always professional, on time, and answered things honestly. From the start and during the 14 months it went on - Tom was very upfront and honest with me about the possible outcomes. The result was better than I had hoped for. Tom really over-delivered. HIGHLY RECOMMEND. Marcela Giorgi
Adams and Luka were very professional and savvy in the courtroom. When you're in court with Mr. Luka you will think you have the best attorney there. I recommend this law firm. Pioneer Tech
Rich Adams is an outstanding criminal attorney. I have had the opportunity to refer several friends and clients to his practice for handling of criminal matters, and on every occasion he has produced an excellent result. Rich practices with attention to detail, a thorough knowledge of the law, and a passion to defend his clients. I will continue to refer clients to Rich Adams, and would strongly recommend him for your legal needs. Brian Pink