Michael Peter Fitzpatrick, 51, was accused of raping and killing 28-year-old Laura Romines on August 18, 1996, after her boyfriend kicked her out of the motel room where they had been living.
An Irish citizen, he was born in the U.S. but his family are from Tipperary.
Formerly of Spring Hill, in Hernando County, Florida, Fitzpatrick was convicted in March 2001 and has spent 12 years on death row.
In June Florida Supreme Court ordered a retrial after it was concluded that Fitzpatrick’s defence attorney was ineffective.
"Ineffective assistance compromises not only the trial, but the entire judicial process," the ruling said.
The court ruled that the accused attorney had failed to consult with experts on DNA and other forensic evidence used against him.
Now Hannah Gorman, caseworker from the UK charity Reprieve, has called on the Irish government to do to help Fitzpatrick's plight.
“Michael’s lawyers completely failed him during his first trial over a decade over,” she told RTE’s Morning Ireland program.
“All evidence against Michael is circumstantial.
“The urgency here is that the trial is due to start Monday and Ireland hasn’t provided assistance to Michael Fitzpatrick and there was an enormous amount that they could do.
“As an Irish citizen, Michael is entitled to consular protection.
“A great start would be to get written representations ready for the court on Monday.”
Fitzpatrick has claimed his innocence throughout.
"I did not kill or cause any harm to Laura Romines," Fitzpatrick said in a hearing in 2001.
The victim was found naked with a slit throat on the side of a rural Land O' Lakes road in August 1996. She died three weeks later, NBC Miami reports.
Fitzpatrick was working as a pizza delivery man at the time and admitted giving the young woman a ride from a convenience store to a motel, where he claims they had consensual sex.
Due to witnesses at the motel who saw Fitzpatrick with Romines on the night in question, police began to focus on Fitzpatrick as the primary suspect.
According to the Innocence Project Fitzpatrick's new attorneys at the Capital Collateral Regional Counsels (CCRC) in Tampa conducted additional DNA testing and hired several experts that together, undermined the prosecution's claims.
The accused's mother Mary Lewis is originally from Ireland.