Mr Winter, originally from Tunbridge Wells, had moved to Miami in 2007 and married the ex-wife of Palacio, a fraud investigator for Citibank.
The graphic designer, 42, was in the process of applying for US residency and had planned to open up a bed and breakfast with his American wife Jennifer, who he met online via a gaming website.
But in October 2008, as Mr and Mrs Winter were dropping off her twins at the house of Palacio, an argument broke out. Palacio, 46, opened fire and shot Mr Winter six times, including twice in the back.
During the trial, Mrs Winter told the court: "He walked up to my husband after he was laying face down and he shot him more in the back, after he was already dead – he shot him more in the back."
She wept as she described the moment after the shooting, and said: "Why did you do this? Why did you kill my husband? How could you do this? Then he just smiled like he was so proud of himself."
Palacio, who had worked for Citibank for 25 years, had claimed he fired in self-defence because he thought Mr Winter was reaching for a weapon.
Mr Palacio's daughter, who was seven at the time of the murder, told the court: "Chris started shooting. He was shooting at Paul."
She said: "I heard the gun being fired. And he fell. He fell to the ground. The gun was fired more than once. I heard a loud sound."
Palacio has been charged with second degree murder, after the jury accepted he may have felt threatened. The charge carries a mandatory life sentence, and Palacio will serve a minimum of 20 years.
Palacio was also convicted of two counts of child abuse, as a result of his children having witnessed the shooting.
