Can DNA Alone Convict Someone of a Crime in Florida?

September 5, 2025 Don Pumphrey, Jr. Criminal Defense Social Share

Imagine a defendant is on trial in Florida. No evidence connects him to the scene of a crime. No eyewitnesses, camera footage, or anything of the sort can definitively identify him. However, the State produces evidence that the defendant’s DNA was found at the scene. Based on the DNA alone, a jury convicts him.

Can this happen in Florida? The answer is yes, DNA can serve as the only evidence of guilt in some Florida criminal cases. However, a guilty verdict rendered based on “DNA alone” can only stand if every reasonable hypothesis of a defendant’s innocence has been excluded. 

This blog will explore whether and when the presence of a defendant’s DNA alone can result in a conviction for a criminal offense in Florida.

Though DNA in criminal cases is often considered reliable evidence, there are serious problems with relying only on the presence of DNA in certain cases. While DNA can sometimes be strong circumstantial evidence of guilt, it’s often insufficient to meet the “beyond a reasonable doubt” standard required to convict someone.

There are many reasons why using the presence of DNA may be risky or ill-advised in obtaining a criminal conviction, in the absence of any other evidence. These reasons include:

• Secondary transfers: DNA can be moved unintentionally (e.g. if someone touched a fork and the fork fell on the floor, DNA ends up on the floor without someone touching it directly).
• Time factor: The presence of DNA does not tell investigators when the DNA is deposited. DNA may mistakenly be thought to mean recent contact between the suspect and a person or object, but this is not always the case.
• Mixed samples: If there is more than one contributor to a DNA sample (e.g. multiple DNA profiles found on a surface), this can complicate interpretation of the results and may result in a wrongful arrest depending on the circumstances (e.g. two DNA profiles on a gun, State infers #1 was the shooter when it was actually #2).
• Lab errors: If DNA samples are mislabeled, contaminated, or interpreted improperly, this can lead to serious errors at trial if DNA is relied upon for a conviction.

Despite this, there are some cases where DNA could automatically eliminate any reasonable hypothesis of a conviction. This is the key question in whether “DNA alone” can convict someone in Florida – there must be no reasonable hypothesis of innocence that can explain the DNA’s presence. State v. Sephes, 262 So.3d 811 (Fla. 4th DCA 2019).

If the State’s case requires “pyramiding of assumptions or inferences in order to arrive at the conclusion of guilt,” DNA’s presence alone cannot serve as the basis for conviction. Brown v. State, 672 So.2d 648, 650 (Fla. 4th DCA 1996). 

An example of this “inference stacking” would be police finding a drop of blood on a park bench after a mugging. DNA matches B, and he is arrested. The “inference stack” here would be that B bled on the bench during the crime (not during another part of the day), that he was the one who committed the mugging (not the victim), and nobody else used the bench before or after.

In cases like this, Florida’s courts generally will not permit a conviction based on the presence of DNA without any other evidence.

There are plenty of reasonable hypotheses of innocence here, including:

• B was the victim of the crime and left before investigators got there, so they did not know who was targeted
• B had a cut and bled on the bench at an earlier point in the day
• B gave an object to someone that he bled on slightly, and it dripped onto the bench

Without additional corroboration that B committed the mugging, these “reasonable hypotheses” of innocence preclude B’s conviction (Sephes). Generally, the more “inference stacking” the State must do to conclusively tie DNA to a crime, the more likely it is that a reasonable hypothesis of innocence exists (which prevents conviction based on DNA alone).

In State v. Sephes, the 4th District Court of Appeal applied this standard to a charge of illegal firearm possession by a convicted felon. Though Sephes’s conviction was reinstated after the State appealed because other evidence tied him to the gun he was alleged to have unlawfully possessed, the court reiterated that “DNA alone” would’ve been legally insufficient.

The court noted that if DNA was the only evidence that was introduced to connect Sephes to the gun, the following two reasonable hypotheses of innocence would’ve existed:

• Sephes touched the gun before he was ever prohibited from owning it and has not possessed it since, but his DNA remained on it
• Sephes was near the gun and through a DNA transfer via shedding or contact with another object, his DNA ended up on the weapon

Given Sephes, examples of when the presence of DNA alone would not be sufficient to convict someone of a crime include:

• C ate at a restaurant the same day it was robbed. The officers swab a counter and C’s DNA comes back. C is arrested and charged with the robbery.
• G is accused of slapping H, who lives with him. There aren’t signs of injury, but H submits to a DNA swab. G’s DNA is found on her cheek, and G is charged.
• Police recover a vehicle abandoned in a parking lot two days after it was stolen from a driver at a gas station. They swab the steering wheel and K’s DNA comes back a match. K is charged with carjacking.

In each of these cases, additional evidence (e.g. surveillance videos, witness testimony, etc.) could support a conviction. However, if the DNA itself is the only evidence that exists, this fails to exclude reasonable hypotheses of innocence.

In each of these cases, a reasonable hypothesis of innocence would include:

• C was simply a customer at the restaurant, and his DNA shed on the counter while he was waiting for food or ordering
• G’s DNA ended up on H’s cheek through a routine transfer, such as touching the same object or sleeping on the same bed
• K drove the stolen car at another time and his DNA remained on the steering wheel, but he did not commit the carjacking

There are situations in which the presence of DNA may by itself exclude every reasonable hypothesis of innocence.

This is particularly common if there is no lawful explanation for the DNA’s presence and the odds of a random match are extremely low. Hypothetical examples include:

• Montana resident, J, is accused of a Florida murder. J claims he’s never been to Florida or met the alleged victim. However, his DNA is found on the victim’s body with a 1 in 10 billion chance of a random match.
• A rape kit is performed on V after she accuses D of sexual battery. D claims he has never had contact with V. However, D’s sperm cells are found inside V, with a 1 in 100 billion chance of a random match.
• Stabbing victim, R, is found with blood in his wound cavity. Forensic testing shows S’s DNA is in R’s wound, but S claims he has never met or even seen R before.

In each of these examples, there is no “reasonable hypothesis of innocence” that can discount the presence of the defendant’s DNA. Thus, Florida’s courts would allow convictions in cases like the ones above even in the absence of other evidence.

In cases where DNA is the basis of the State’s case against a defendant, it is crucial for a Florida criminal defense attorney to challenge its admission.

Grounds on which to do so may include any of the following, depending on the facts of a case:

• Chain of custody challenges: If there was potential tampering, contamination or mishandling of evidence, DNA can be excluded on this basis. The defense must show “probable” tampering, contamination or mishandling. If this is shown and the State fails to rebut the allegation, the evidence is excluded.  Murray v. State, 838 So.2d 1073 (Fla. 2002)
• Daubert challenges: Under Fla. Stat. 90.702, DNA evidence must be collected in a manner that is scientifically reliable. Testimony relating to the DNA can only be admitted if based on sufficient facts and data, the product of reliable principles and methods, reliably applied to the facts of the case.
• 90.403 challenges: Under Fla. Stat. 90.403, otherwise relevant evidence (including DNA) may be excluded if its probative (evidentiary) value is substantially outweighed by the danger of unfair prejudice, confusion, needlessly cumulative presentation of evidence, or misleading the jury.
• Illegally obtained evidence: If police failed to obtain a warrant or used improper methods to get a DNA swab (e.g. coercion or threats), the sample may be suppressed as “fruit of the poisonous tree,” precluding its use at trial (Wong Sun v. U.S.).

In sum, the presence of DNA alone can serve as the basis for a criminal conviction in Florida – but not always. This is only the case when the presence of DNA excludes every reasonable hypothesis of the defendant’s innocence.

Where DNA might be explained by innocent contact, incidental transfer, or prior lawful presence, a conviction cannot stand if no other evidence is presented. But when DNA is found in a location where no innocent explanation exists (e.g. at a murder scene in a state someone claims to have never been to), this can support a conviction by itself.

If someone is arrested and formally charged in Florida and wishes to challenge DNA evidence, it is critical to find experienced and trusted legal representation as soon as possible. This decision could make the difference in whether or not someone faces a lengthy prison term and hefty fines.

Criminal Defense Attorney in Tallahassee, FL

Don Pumphrey, Jr. is a Former Prosecutor, Former State Police Officer, Lifetime Member of the Florida Association of Criminal Defense Lawyers; for over 25 years as a private defense attorney who is Trusted, Experienced, Aggressive in Criminal Defense as a Trial Attorney, Criminal Lawyer, Criminal Defense Lawyer for the accused in Florida State Courts located in Tallahassee, Florida but handling cases throughout the State of Florida.

Don Pumphrey, Jr. and the Tallahassee criminal defense lawyers at Pumphrey Law have decades of experience fighting drug charges on behalf of clients and winning. Call Pumphrey Law now at (850) 681-7777 to learn more about what we can do for you. Our lawyers will be happy to provide you with a free consultation.

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