Aaron Fraser was just 3 when his mother disappeared in 1993 and he told the authorities that his father had done something to hurt her.

“Daddy shot Mommy,” he said then, according to court documents. “Daddy placed Mommy in time out.”

That account, from the mouth of a child, was not enough to solve the case. But as an adult, Mr. Fraser would find the evidence that would.

The discovery came after more than two decades, years in which Mr. Fraser was adopted, won a wrongful death judgment against his biological father and acquired the rights to his childhood home in Jacksonville, Fla. He was doing renovations on the property in 2014 when he struck something in the ground and realized he had stumbled upon his mother’s remains.

His testimony, from 1993 and now, bookended a cold case that went to trial this week, 26 years after Mr. Fraser’s mother, Bonnie Haim, disappeared. On Friday, a jury found Mr. Fraser’s biological father, Michael Haim, 52, guilty of second-degree murder.