Robert DuBoise, convicted in 1983 for a murder in Tampa, could be released Thursday after DNA evidence exonerated him. (Florida Department of Corrections)

During 37 years in prison for the rape and murder of a 19-year-old woman in Tampa, Robert DuBoise never stopped trying to prove his innocence. When he was first arrested in 1983, he willingly submitted to a dental examination, telling police: “I want to do it and get it over with. I’ll prove to you I did not bite that girl.”

But DuBoise was convicted and sentenced to death. The Florida Supreme Court later reduced his sentence to life.

Finally, the state began listening to his claims that authorities had the wrong man. Earlier this month, the rape kit from the 1983 attack was discovered in a medical examiner’s office, and DNA was extracted and tested. Late last Thursday, the Hillsborough County prosecutor’s office received the results: DuBoise was excluded as an attacker. A “person of interest” has been identified through the DNA and is now being investigated.

The prosecutors, guided by years of research from the Innocence Project, sent the case to a panel of experts who all agreed: DuBoise was wrongly convicted. And on Wednesday, six days after the DNA test results were received, Hillsborough State Attorney Andrew Warren filed a motion to immediately reduce DuBoise’s sentence to “time served,” hoping to have him freed from prison by a judge on Thursday.

“This is painful and tragic, but it’s the truth,” Warren said. “When you tell the truth, justice is done. … For 37 years, we had an innocent man locked up for a crime that he did not commit, while the real perpetrator was never held accountable for this horrific crime. … I apologize to Mr. DuBoise on behalf of the entire criminal justice system.”

DuBoise, 55, incarcerated at Hardee Correctional Institution in Bowling Green, Fla., was not available for comment. When he got the call Monday from his attorneys, “he was overjoyed,” said the Innocence Project’s Susan Friedman, who handled the case with local support from Seth Miller of the Innocence Project of Florida. “He told me it was like waking up from a nightmare. Remember, he was on death row at one point.”

Barbara Grams was 19 when she was slain in Tampa in 1983. Prosecutors now say the man convicted of her murder is innocent. (Hillsborough County state attorney's office)

DuBoise was convicted of killing 19-year-old Barbara Grams in August 1983 as she walked home from work in central Tampa. The case against DuBoise hinged on two things: bite-mark evidence, now widely discredited as a scientific means of identification, and testimony from a jailhouse informant, a strategy also believed to be frequently misused by police and prosecutors.

The bite-mark evidence was presented by dentist Richard R. Souviron, who also testified about bite marks in the trial of serial killer Ted Bundy. But an expert who reviewed the evidence in the DuBoise case now believes that the mark on Grams’s cheek was not even a bite mark.

Souviron has acknowledged that he has overstated the certainty of bite-mark matches in court testimony over the years, as science has determined that many bite patterns can be similar, that bites in skin may not be an exact capture of a bite pattern and that people’s bite patterns change over time.

Souviron is still a practicing dentist in Florida and still offers his testimony in cases. He said he and a dental expert for the defense both thought the mark on Grams’s cheek was a bite mark. Souviron also said he hoped his testimony did not wrongly convict DuBoise.

“I hope not,” Souviron said in a telephone interview. “God I hope not. If he’s innocent, he deserves to be out.”

Souviron lauded the Innocence Project for raising the scientific bar on dental testimony and said dental experts no longer conclude a mark matches “to a reasonable degree of dental certainty,” as he did at DuBoise’s trial in 1985. “That has been changed to say we cannot eliminate that person.” He said dentists can no longer definitively match teeth patterns with bite marks in most cases.

“We can’t do that,” Souviron said. “It’s not right, unless you have a bite mark like in the Bundy case,” which he said was clearly identifiable as coming from the notorious serial killer.

Warren said in a news conference that after he started a conviction review unit in late 2018 he received 250 petitions seeking reviews. Among those, DuBoise is the 20th person to be exonerated, Warren said. Conviction integrity units have been launched in prosecutors’ offices throughout the country in recent years, leading to hundreds of exonerations, including 165 in 2018 alone.

After Grams was killed, police began taking teeth impressions of numerous people in the Tampa area, using wax. DuBoise, then 18, submitted to that process. Police said they supplied those wax impressions to Souviron, who told them that DuBoise was a match. Court records show that police then obtained a search warrant to obtain a more lasting impression of DuBoise’s teeth but that he voluntarily cooperated.

Souviron told the police DuBoise again was a match. DuBoise was charged with murder and sexual battery.

After his arrest, DuBoise spent time in the Hillsborough County jail with a man named Claude Butler. Butler claimed that DuBoise told him that two other men had killed Grams by beating her in the head, while DuBoise raped her.

Authorities said Butler was in jail facing trial with a possibility of multiple life sentences for kidnapping, armed robbery and battery on a law enforcement officer. Instead, the Innocence Project found, after Butler cooperated with police, he received a five-year sentence. Once the trial was over, Hillsborough County prosecutors asked a judge to release Butler immediately, and he was freed after 16 months. The men Butler claimed DuBoise had named as the actual killers were never prosecuted.

“His testimony had significant inconsistencies,” Warren said, “and more importantly, the new DNA evidence clearly refutes his testimony. He named three men who were supposedly involved in the rape and murder, and the DNA does not match any of them.”

After Souviron and Butler testified against DuBoise, a jury convicted him and sentenced him to life in prison. But Circuit Judge Harry Lee Coe III overrode the jury and sentenced DuBoise to death in 1985. In 1988, the Florida Supreme Court ruled that the jury’s sentence was appropriate for someone who was not accused of being the actual killer and ordered Coe to resentence DuBoise to life.

Warren said he had spoken with Grams’s family. “For 37 years, her family was given false closure on a false story,” Warren said. “I spoke to them and apologized to them.” He said they did not want to speak publicly.

The Innocence Project took on DuBoise’s case in 2018, Friedman said, and submitted it to the Hillsborough conviction review unit in September 2019 after digging into the jailhouse informant, Butler. Friedman noted that DuBoise first filed a motion seeking DNA testing in 2006 but was told the evidence had been destroyed in 1990.

“Robert constantly said to us: ‘What about the DNA? What about the DNA?’” Friedman said. “He knew that would prove his innocence and the question would be over. When I told him they found the [rape kit] slides, he was so happy he would finally be cleared.”

Warren said an investigation was ongoing looking at the “person of interest” developed as a “major contributor” to the DNA found on the victim. He said the person was not a threat to the public but declined to elaborate.

The motion to reduce DuBoise’s sentence was scheduled to be heard in Hillsborough County Circuit Court on Thursday morning. Warren said that if it is granted, he hopes for DuBoise to be released later Thursday. Then the prosecutors plan to file a further motion to completely exonerate DuBoise.