AUTHOR Jack Ross listened intently as a tattooed prison officer unabashedly described the mental tortures inflicted on Death Row inmates.
Guards would walk down the stale sweat-smelling corridor in the middle of the night tapping noisily on the cell bars to disturb prisoners' sleep.
Another tactic was to drive inmates crazy calling into the cells in the early hours feigning kindly checks to make sure they were all right.
As he heard the guard's boasts in the Florida diner, Jack remained dispassionate, drawing on his long experience as a reporter.
These men worked in a pressure-cooker environment with murderers, rapists and psychopaths, where intimidation was part of the culture, he reasoned.
Back in Edinburgh, where we meet in the Radisson Hotel, newly-published author Jack recalls: "The prison officers said these guys were filth.
"They were guys my age, very pleasant and God-fearing, but they see it as an eye for an eye. They believe they are doing God's work."
There's still plenty of the journalist about Jack, 44, whose occasional indiscretions during our interview are followed with a swift "that's off the record".
He is here to discuss his debut novel, Requiem, about an elderly Scots man on Death Row in Florida, which he flew to Miami with his wife Susan, 41, to research.
The American crime novel is the first in a two-book deal and the BBC has snapped up the audio rights to the book, while foreign rights have so far been sold in Germany and Romania.
The freelance journalist and former Evening News reporter – real name John Bald – had just interviewed the mother of ex-Death Row Scot Kenny Richey when his lightbulb moment occurred.
It was back in 2000 and he'd been touched by Eileen Richey's account of her upset after visiting Kenny, who she saw chained up like an animal on Death Row.
"I was coming back in the early afternoon from her house in Dalry, past the Diggers' pub, when I suddenly started thinking about a Scots guy on Death Row, with an American journalist investigating; an old guy and a young female reporter to make her a contrast.
"By the time I got home to Roseburn, instead of writing up the interview with Eileen Richey I cracked on sketching out the idea.
"Writing took hold of me and before I knew it, it was 11pm and I'd done the prologue."
An avid reader of American crime fiction by authors such as James Lee Burke, Jack decided he needed to go to Miami to get a feel for the gritty world he wanted to portray.
Through friends there he set up interviews with prison officers and an undercover policeman, who drove him around, showing him the city's seedier side.
"Crime levels were epidemic in places like Liberty City and Overtown. There was block after block of decrepit buildings and no infrastructure. Certain taxis were relied on to service black areas and white taxi drivers were terrified to go there. It was off-the-scale deprivation."
Jack decided his protagonist, Deborah Jones, would be a middle-class black Miami Herald reporter, gaining awareness of this underworld by playing in a football team with underprivileged women.
She is drawn to investigate the case of William Craig, from East Lothian, on Death Row for killing the son of a senator who savagely raped his granddaughter.
With limited time before William is due to be executed Deborah has to work fast, all the while incurring the dangerous wrath of Senator O'Neill, one of the most powerful men in town.
Following his Miami visit, first-time author Jack was so fired up that, caffeine-fuelled, he finished his first draft of Requiem at his flat in Roseburn in just a month.
After that he moved to Dunfermline, where he painstakingly re-drafted, before looking for an agent – which was where his real struggle began.
He found an agent in New York, but after 18 months of changes she asked him to rip it up and start again.
"I did," says Jack, "Though it was soul-destroying, it brought more focus to it."
He believed American agents would be more interested in a crime novel set there. However, with still no luck after changing to an agent in Boston, he e-mailed Caradoc King, the chairman of AP Watt, who, among others, represents Nicholas Evans, author of The Horse Whisperer.
"Within 48 hours he told me to come to London and I got the next flight."
Frustratingly, more than five years after starting the novel, his new agent also wanted Jack to make a few tweaks. This might have been a bigger blow if he hadn't been used to years of editorial changes to his work as a journalist. "You have to be big enough to accept that. If you have a thin skin, don't get into writing a book – or journalism," he shrugs, taking a sip of his cappuccino.
So has the Lothian author managed to convince American readers with his portrayal of life across the Atlantic?
"I've spoken to a few people who have read it out there and they were bowled over," says Jack, with no false modesty, "They thought it was sensational, really evocative of Miami."
The hardback is already in bookshops, while the paperback is due for publication next February by Arrow, who publish John Grisham. He smiles: "That's hugely prestigious. John Grisham is a genius."
Jack says he felt no need to visit Death Row personally to write the book, preferring to interview guards and families of inmates.
The father-of-two has done numerous tours of prisons, from Saughton to Barlinnie, but says the US prison system he's portrayed is vastly different, based on gangs and racial lines.
Ever the journalist, he adds: "I was interested in getting stories from real people, not a sanitised tour. I wanted a real gut feeling, not what they wanted to see."
As for the source of his inspiration, he has never met Kenny Richey and has no plans to do so. "But I wish him well".
• Requiem by Jack Ross is published by Hutchinson, priced at 12.99