The Use of Fingerprints in a Criminal Case

When you are arrested in Cincinnati, the police will generally take your fingerprints. If you have not been arrested, the officers could ask you to consent to be fingerprinted. They may want the fingerprints to compare to the prints taken from a crime scene. 

If you refuse to provide your fingerprints, the officers could ask a judge to sign a search warrant for your fingerprints if you refuse to provide them. Continuing to refuse to provide your prints could result in a contempt of court charge, which means you can be arrested. The arrest would then allow the officers to get your fingerprints.

In some cases, law enforcement officers might trick you into providing your prints. For example, they might offer you a drink to get your prints on a glass, or they might pick up trash from the garbage to obtain your prints. 

Generally, once you are fingerprinted as an adult, your fingerprints are in the system. Therefore, even if you are acquitted or the court dismisses the criminal case, your prints remain in the system as part of your criminal history. That is true even if you qualify for expungement.

Three Types of Fingerprints Used in Criminal Cases

There are three types of fingerprints law enforcement officers gather at the scene of a crime to use when investigating crimes. The prosecutor may use the fingerprints as evidence during a trial. 

Patent Prints

A patent fingerprint is left on a hard surface by touching the surface with your fingers. The prints are visible on the hard surface. You can photograph the fingerprints to capture the detail without using chemicals to improve visibility.

Patent prints can also be left in various materials, such as dust, blood, and paint. Good lighting is necessary to see the print. A flashlight can be helpful when searching for patent fingerprints.

Latent Print

Latent fingerprints are not visible. They are prints left on surfaces by the sweat or oils on the fingers. A chemical or physical process must be used to enhance a latent print so that it can be seen on the surface.

Plastic Print

Three Types of Fingerprints Used in Criminal Cases

A plastic fingerprint is a three-dimensional print. Plastic prints can be left on soft surfaces that allow the raised friction ridges to create a mold when the finger is pushed into the material. Examples of substances that could have a plastic print include wax, heavy grease, clay, soft wax, melted plastic, putty, and tacky paint. 

Plastic prints are already visible. Therefore, an officer can use a camera to take a picture of the print with oblique lighting to enhance the contrast of the furrows and ridges. A silicone-type material can also be used to create a cast of the fingerprint. 

Why Do Police Officers Analyze Fingerprints from a Crime Scene?

Crime scene investigators search for prints at the scene of a crime. Then, they document the fingerprints as evidence and try to “lift” the prints, make molds, and/or photograph the prints. 

Fingerprints can be used to search for people who were at the crime scene. The officers search for matching prints through the IAFIS system. If they find a matching fingerprint, they can identify a potential criminal suspect.

At trial, prosecutors use fingerprint evidence to allege the defendant was at the crime scene. The fingerprint might not prove the person committed the crime, but it can help establish the opportunity to commit the crime.

What Does It Mean if Fingerprints “Match” the Defendant’s Prints?

Fingerprints do not change during your life, and fingerprint patterns are unique. Even twins have different fingerprints. Therefore, finding a matching set of fingerprints at the crime scene can be compelling evidence at trial.

However, fingerprint evidence is not perfect. There are several ways to challenge fingerprint evidence used in a criminal case. 

An expert witness or lab analyst often says that the fingerprints collected at the crime scene “match” the defendant’s fingerprints. However, the witness is not stating that the prints are from the same person.

Instead, the witness is stating that the two fingerprints have some unique characteristics that match. While fingerprints can be accurate, there is still room for mistakes and incorrect interpretations of the evidence. 

Experts disagree about how many unique points must match before you can declare that a fingerprint belongs to a specific person. Some fingerprint experts state that a match must have 12 points in common. Other experts state at least 20 points need to be in common to declare a fingerprint match. 

Furthermore, human error when processing fingerprints can make the prints unreliable. A criminal defense lawyer can generally find some fault in the matching process or the process used to collect the fingerprints.

Another problem with “matching” fingerprints is that it can be nearly impossible to determine the age of the fingerprint. The defendant could have been at the crime scene weeks before the crime was committed. Therefore, the fingerprints at the scene do not indicate the person was at the scene when the crime was committed. 

A defense attorney may hire a fingerprint expert to testify about mistakes and lack of sufficient matching points to claim the print was the defendant’s fingerprint. Challenges are very common when the police officers only find partial fingerprints at the crime scene. 

What Should You Do if the Police Tell You They Found Your Fingerprints at the Crime Scene?

Even though your fingerprints were at the crime scene, it does not prove that you committed the crime. The state must present sufficient evidence during the trial to convince jurors you are guilty of the alleged crime. 

A criminal defense lawyer searches for evidence that can help with your case. Your lawyer also develops an effective defense strategy based on the facts of your case. 

It is never wise to talk to police officers without a lawyer present, even if you are innocent. The officers can lie. They might tell you that they have your fingerprints as a way to get you to tell them more about the case.

The best thing you can do is to ask for a criminal defense lawyer. Otherwise, remain quiet. The more you talk to the officers, the more chance you will say something that could make it very difficult to defend you against the criminal charges. 

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Working with an experienced criminal defense lawyer can give you a better chance of beating the criminal charges you’re facing. Contact our law firm to schedule a free consultation with one of our experienced criminal defense attorneys.