Criminal investigators and prosecutors have always used whatever technology is available to assist them in finding and prosecuting alleged criminal activity. Technology has come a long way in the past century. Instead of using magnifying glasses and dusting for fingerprints, today’s detectives utilize cutting-edge technology to identify and prosecute criminal suspects. The advent of DNA technology in the past 40 years has revolutionized criminal investigation. New technologies are not always reliable, however, and “junk science” has been used in the past by prosecutors when securing illegitimate convictions. The Texas Court of Appeals recently addressed a defendant’s challenge to a relatively new method of DNA analysis.
The defendant in the recently decided case was arrested and charged with sexual assault after an investigation pointed to him as a suspect in the rape of a neighbor. Police recovered many pieces of evidence to link the suspect to the crime, and biological samples were taken from the defendant to compare with evidence left at the crime scene using DNA testing technology. During the trial, the prosecutor called an expert witness to discuss the results of the DNA testing. The DNA testing for this case was performed using a technology known as Y-STR testing. According to the witness’s testimony, the defendant’s DNA matched the semen recovered from the crime scene. The expert testified that the chances of the DNA being from another unrelated person from the suspect were 1/237,000,000,000,000,000,000,000,000,000,000. Based on the testimony from the expert, as well as the other evidence offered at trial, the defendant was convicted of the crimes.
The defendant appealed his conviction on several grounds, mostly arguing that the DNA testing was unreliable and that the Y-STR testing technology used by the prosecutor’s expert was not proven to be accurate. On appeal, the high court rejected the defense’s arguments, noting that settled Texas law accepts DNA testing as a reliable method of identification, and previous Texas Supreme Court decisions have allowed the admission of Y-STR evidence that was even less compelling than that offered in this case. As a result of the high court’s ruling, the defendant’s conviction will stand