Texas DNA Evidence & Collection Laws in Sex Assault Cases

Do Texans have a right to reject DNA samples in a sex crime case?

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You see it routinely in movies and on TV series: DNA samples leading to criminal charges and convictions.

Yet DNA samples may not be handled properly, and they may not tell the whole story of an alleged crime. So the question arises:

Do Texans have a right to reject having DNA samples collected in a sex crime case?

DNA samples are a key to sex assault investigations

According to the Texas Attorney General’s office:

“Few other criminal offenses require as extensive an examination and collection of evidence as a sexual assault. And, but for an occasional assault case, no other crime collects as much evidence from a live person.”

That person can be the alleged victim as well as the alleged assailant.

When it is the alleged victim, the office says:

“The examination and collection of physical evidence in sexual assault cases has fallen to physicians and nurses in hospital emergency rooms and pediatric units. The role of medical personnel in this process often can be the key to successful prosecution and can help to promote early emotional recovery for the patient.”


It goes on to say that evidence from the alleged offender:

“...often may be found on the body and clothing of the patient. When immediate medical attention is received, the chances increase that some type of injury or physical evidence may be found. Conversely, the chances of finding injury or physical evidence decrease in direct proportion to the length of time which elapses between the assault and the examination.”


When DNA material is collected in this way, and when an alleged assailant has been identified, police may arrest that person and demand DNA material from him or her as well, to see if it corresponds.

But does an accused person then have a right to refuse providing such DNA samples?

State has some right to take DNA samples

Depending on the crime, the state of Texas has some right to take DNA samples from the accused person or suspect, but not a complete right. The timing and the means for collecting the DNA sample depend on the charge and on the person’s criminal record.

If an accused person is indicted or arrested for a violent or sex-related crime such as sexual assault, the state has the legal right to take a DNA sample via blood or cheek swab (also is known as a buccal swab).

Such samples can be taken at arrest or booking (when information about an arrest is recorded at a police station) or at arraignment (a hearing in court when a person is formally charged). DNA sample collection is handled at arraignment if the person has no previous convictions. If the accused has prior convictions, the sample is taken at booking.

Police can also take a DNA sample if they have a search warrant to do so or if they have what is known as “probable cause” that the suspect committed the crime. A court may also order that a blood sample with DNA be collected after a person has been convicted of a felony in Texas.

A skilled sex crime defense lawyer can use DNA and other means to defend a suspect’s legal rights in a sexual assault case.


What is DNA?

As for what is DNA, it stands for deoxyribonucleic acid, which is the molecule that contains the genetic code of a person. Each cell in a person’s body has the microscopic genetic material known as DNA, also referred to as the molecule of life, and that material identifies individuals precisely—a kind of genetic fingerprint.

Almost every cell in a person’s body has the same DNA, which is unique to that person.

The important distinction is that DNA is in cells of human tissue, and those cells can be found in various ways and various places—including tissue, skin and bone marrow.

For a criminal investigation, such DNA can be collected and examined in various ways. It’s often collected via saliva or blood. Urine also has small amounts of DNA in it, but not nearly as much DNA as is found in saliva or blood. Also, DNA deteriorates more quickly in urine.

In addition, a human cell may be found in another substance. In addition to saliva, blood and urine, cells featuring DNA may also be found in perspiration (sweat), mucus, earwax, vomit, feces, hair and tears.

For a sexual assault case, DNA can be found in spermatozoa, semin or seminal plasma. But lack of such evidence doesn’t necessarily mean the suspect is innocent.

The Texas Attorney General’s office states that a lack of spermatozoa “is not conclusive evidence that an assault did not occur: It only means that spermatozoa may have been destroyed after being deposited or that it may never have been present.”


The AG’s office goes on to say that many sexual assault offenders “are sexually dysfunctional” and do not ejaculate during the assault in up to half of sexual assault cases.

“Additionally, offenders may use a prophylactic, have a low sperm count (frequent with heavy drug or alcohol use), ejaculate somewhere other than in an orifice or on the patient's clothes or body, or penetration could have been by an object other than a penis.”

“There could also have been a significant time delay between the assault and the collection of specimens. The patient could have inadvertently cleaned or washed away the semen, or the specimens could have been collected improperly.”


Thus, while spermatozoa can be used as evidence in a sex crime case, it also may be difficult to use as DNA proof of a sex crime.

DNA can be used to place a person at the scene of a crime, even if it does not prove that the person committed the crime. Since DNA exists in some form in almost every cell of a person’s body, a strand of hair or a tiny bit of skin at the scene can place the accused at the scene of the crime.

Texas has a DNA database

Since 1995, the state of Texas has maintained a computerized DNA database to assist state, local and federal law enforcement agencies in investigating and prosecuting offenses for which biological evidence is recovered.

Prison inmates must provide DNA samples if ordered to do so by a court or if they have been convicted of certain crimes such as murder, aggravated assault or a sex offense which requires the offender to register as a sex offender.

This database, which is kept by the Texas Department of Public Safety, can be used to help identify possible offenders in other crimes.

According to the state, DNA test results are often reported as an “exclusion” or an “inclusion.” In a criminal case, an exclusion means that the suspect’s DNA does not match the DNA obtained from the crime scene. Conversely, an inclusion (also known as a match), means that DNA evidence from a crime scene matches that of a known person or suspect.

When the state takes a DNA sample, it is retained in the database so that it can be used to match the accused to the crime in question or to other incidents.


However, if the accused person is not charged, if the charge no longer qualifies for compulsory collection of a DNA sample or if he or she is found not guilty in court, then the state of Texas provides for automatic expungement, or removal, of the DNA information from its statewide DNA database. In addition, the DNA sample itself is destroyed.

DNA evidence can help the accused or convicted

DNA evidence doesn’t just help one side. It may also be used to exonerate a person who was wrongfully convicted or accused.

In Texas, post-conviction testing of DNA evidence has led to gubernatorial pardons and to the release of convicted persons from prison.


Indeed, post-conviction collection of DNA evidence reportedly has been involved in about 25 percent of all exonerations in the United States since 1989, the year in which DNA began being used as evidence. With DNA samples, a criminal defense lawyer can go back to years-old events to find proof of innocence.

Consult a Texas sexual assault defense lawyer

Regardless of whether or not DNA is a factor in your case, if you or a member of your family faces an accusation, charge or possible charge of sexual assault, get an experienced and knowledgeable sexual assault defense lawyer to fight for and protect your legal rights.

Our criminal defense law firm handles such cases. Whether you live in Houston, The Woodlands, Conroe, Sugar Land or elsewhere in Fort Bend County, Montgomery County or Harris County, contact us today at the Neal Davis Law Firm to arrange a confidential consultation of your case.

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