As avid Agatha Christie fans and founder members of the Florida Grim Death Club, Trepal and his wife Diana were in regular demand organising murder mystery weekends in which participants were given a script and acted out a grisly plot.
The victims always met a sticky end — there were drownings, beatings, shootings and strangulations. But at least half died from poisonings ... George Trepal's favourite form of murder.
As Ernest Prince, a fellow-member of the Grim Death Club, based in Bartow, Florida, was to recall: "If someone was going to be poisoned, George would find out exactly what symptoms they would get and how the crime could be investigated. He was always a real perfectionist when it came to poison. He seemed fascinated by it."
George Trepal was pretty smart. He was a member of the high-intelligence club Mensa. Diana Trepal was an orthopaedic surgeon and their inner circle of friends included nuclear scientists, college professors, writers and academics.
"Conversation at their dinner parties was pretty cerebral," remembered Nigel Walsh, who lived across the road from the Trepals' expensive split-level home. "We all knew about George's preoccupation with murder. It was just regarded as a quaint intellectual exercise. I thought him a real fun guy."
But the family who lived next door, Paul and Peggy Carr and their sons Duane and Travis, knew little about the pleasant side of George Trepal's nature.
For the six years they had been neighbours he had complained constantly about their noisy music, late-night parties and trespassing on his land. There was a long-running dispute over the sitting of a fence and damage that Trepal claimed had been done to his garden by the Carrs' three dogs.
But by October 1988, the Carr family had more to worry about than a neighbours' dispute. Peggy Carr, 45 and previously in good health, began suffering from nausea and aching joints. So did her two sons and a week later all three were in hospital.
The boys recovered slowly from the mystery illness but their mother got worse. After two months she slipped into a coma from which she never recovered. In March 1989 her family took the tragic decision to switch off the life support system and three days later, Peggy was dead.
FBI forensic investigators examined a number of Coke bottles thrown into a garbage container and discovered they had been laced with thallium nitrate, a rare colourless odourless poison banned in America since 1965. One gramme was enough to kill.
Who had been tampering with Coke bottles? An FBI investigation at the bottling plants revealed nothing and the neighbours, including the Trepals, were interviewed in order to eliminate them from the inquiry.
But seasoned detectives felt there was something strange about George Trepal. He seemed excited by the prospect of being interrogated and boasted how much he knew about crime, particularly murder. He told Detective Kevin Barrass: "I have made a study of violent crime and know that if I ever committed murder it would be the perfect one."
Barrass would later tell a court: "He seemed determined to leave us in no doubt that we were in the presence of a superior intellect. I was left feeling that he was desperate to tell us something but knew it would be unwise to do so.
"I later told my superior that I thought we should further investigate Trepal but if possible without his knowing." As a result undercover detective Susan Goreck, 35, was put on the case and instructed to get to know the Trepals and if possible become friendly with them.
Goreck arrived in Bartow posing as a freelance computer-programmer working from home and rented a house near the Trepals. Eventually she was invited to one of George Trepal's murder weekends and was soon a regular attender.
She said later: "I found George Trepal a charming man, interesting to be with and very amusing. It did not take me long to discover that he had an obsession with murder, particularly invol