Investigators used modern genetic genealogy techniques to identify a suspect nearly four decades after the crimes.
WAKEFIELD, R.I. — An Indiana man has been sentenced to consecutive life terms after being convicted of raping and sexually assaulting two girls at knifepoint in Exeter in 1987, ending a cold case that remained unsolved for nearly 38 years.
Frank Joseph Thies was found guilty of multiple felony charges stemming from attacks that occurred on April 12, 1987. Authorities said the case lingered without a suspect for decades despite extensive investigative efforts. The eventual conviction was made possible through advances in DNA testing and genetic genealogy, tools unavailable when the crimes first occurred.
According to prosecutors, two girls, ages 11 and 13, were in a wooded area near Stony Lane when a man approached them with a knife and sexually assaulted them. Investigators responded immediately and launched an extensive search for the suspect. Detectives interviewed witnesses, collected physical evidence and pursued numerous leads throughout the late 1980s and 1990s. Despite those efforts, no suspect was identified. The investigation gradually became classified as a cold case, though authorities continued preserving evidence and reviewing the file. Court records showed the victims remained engaged with investigators over the years and provided assistance whenever new developments emerged.
The breakthrough came decades later when Rhode Island State Police renewed the investigation using advanced forensic testing. Detectives submitted evidence for additional DNA analysis and later employed genetic genealogy to identify potential family relationships connected to the unknown DNA profile. Investigators eventually traced the evidence to Thies, who was living in Indiana. Authorities discovered that he had traveled to Rhode Island in 1987 while attending training at the Naval Justice School in Newport. Detectives subsequently obtained a DNA sample that prosecutors said matched evidence collected from the crime scene. The findings resulted in Thies’ arrest in 2022 and his transfer to Rhode Island for prosecution.
The prosecution presented testimony from investigators, forensic experts and others involved in the case. Jurors heard evidence detailing how technological advances enabled authorities to revisit biological evidence collected nearly four decades earlier. Prosecutors argued that the DNA evidence conclusively identified Thies as the attacker. Defense attorneys challenged aspects of the case, but jurors ultimately returned guilty verdicts. The conviction represented a significant milestone for law enforcement officials who had spent years attempting to identify the perpetrator. Investigators credited careful evidence preservation for making the eventual prosecution possible.
At sentencing, the court imposed two consecutive life sentences. Rhode Island Attorney General Peter Neronha said the outcome reflected the persistence of investigators and the determination of the victims, who waited decades for the case to be resolved. The court also entered a no-contact order barring Thies from contacting either victim. Officials said the sentence ensures that the defendant will remain incarcerated while providing a measure of accountability for crimes committed nearly 40 years ago. Prosecutors noted that many cold cases never reach this stage, making the resolution particularly significant for everyone involved.
The sentencing hearing drew attention from investigators who had worked on different phases of the case over the years. Several retired law enforcement officers followed the proceedings, reflecting the long history of the investigation. Prosecutors said the verdict and sentence demonstrated the value of revisiting unsolved crimes as forensic capabilities continue evolving. Family members of the victims expressed relief that the legal process had finally concluded. The case remained one of Rhode Island’s oldest unresolved sexual assault investigations until the DNA evidence provided the crucial breakthrough.
With sentencing complete, the prosecution has concluded, bringing finality to a case that began with a violent attack in 1987 and ended with a conviction nearly four decades later.
Author note: Last updated June 17, 2026.