Fingerprint Evidence Used in Criminal Trials
Topics covered in this blog:
- What is Fingerprint Evidence?
- How to Collect Fingerprint Evidence
- Why are Fingerprints Used in Criminal Cases?
- Problems with Fingerprint Evidence
- Top Criminal Defense Attorneys in Salt Lake City, Utah
In today’s high-tech criminal investigations, fingerprint evidence may seem old-school. But, while matching fingerprints may not seem as exciting as DNA matching, it continues to be an essential form of evidence in many cases. One benefit of fingerprint evidence is that understanding the little ridges, loops, and whirls that form unique patterns in fingerprints is relatively straightforward for jurors to understand.
How to Collect Fingerprint Evidence
The friction ridges of fingerprints contain tiny lines of pores that excrete sweat. The sweat combines with the body oils and dirt from the environment, becoming a part of the mix. This substance on our fingers produces fingerprints when we touch surfaces. Experts in gathering fingerprint evidence apply chemicals and powders to make the fingerprints visible and even extract them and preserve them.
Some fingerprints are ideally visible after they have been lifted from a surface. Others require fingerprint processing experts to fill in the pattern from fragments by applying digital enhancement techniques. For yet other prints, the specialists use state-of-the-art laser technology to read prints invisible to the eye.
Using the above-described methods, fingerprint experts can collect prints from most surface types and process them sufficiently to identify the individual who left the prints.
Why are Fingerprints Used in Criminal Cases?
The value of fingerprint evidence is based on two essential properties of fingerprints:
- The friction ridge patterns are the unique shapes of the swirls on the fingertips. These do not change throughout a person’s lifetime.
- There are no two people with the same friction ridge pattern on their fingertips. Amazingly, even identical twins do not have matching fingerprints!
How Fingerprint Evidence is Used in Criminal Cases
Law enforcement uses fingerprints found at crime scenes to identify suspects with matching prints. Investigators use expert analysis of comparisons between prints found at crime scenes and digital catalogs of prints in police databases. The FBI’s collection of fingerprints has been built over time to contain millions of sets of prints. There are various reasons why a person’s fingerprints may be on file in the national database:
- The individual may have been fingerprinted when they started working in a type of job that requires it.
- The person may have been fingerprinted when they were arrested.
- Individuals may have been fingerprinted as a child, at the request of his/her parents, for potential help with identification if necessary in a case of abduction.
Problems with Fingerprint Evidence
Court cases involving fingerprint evidence do not necessarily have predictable outcomes, even when the evidence may seem conclusive. There is disagreement among fingerprint experts about the number of points that the two sets of fingerprints must have in common to accurately declare they are a match. Some experts believe that they must find at least 20 points of comparison matching. Others believe that only a minimum of a dozen points must match to confirm that the prints are from the same person.
Another issue regarding the presentation of fingerprint evidence in court is that it is nearly impossible to determine the age of a fingerprint. So, defendants frequently attempt to create doubt by claiming that their fingerprints found at the crime scene were left there at some time before or after the time the crime was committed.
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