A former Nevada prison inmate was convicted Friday in the decades-old hammer and knife murders of three Colorado family members, including a 7-year-old girl. 

Alex Ewing, 60, was found guilty by a jury, a day after closing arguments on Thursday. He was convicted for the 1984 deaths of Debra Bruce Bennett, 27, his wife Debra, 26, and their daughter, Melissa, in the Bennetts' home in the Denver suburb of Aurora.

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Alex Ewing enters the court for his murder trial Tuesday in an Arapahoe County Court in Centennial, Colo. Ewing was convicted Friday of killing Bruce and Debra Bennett and their 7-year-old daughter Melissa in Aurora in January 1984. (Philip B. Poston/Sentinel Colorado via AP, Pool)

Melissa Bennett was also raped, prosecutors said. The couple's 3-year-old daughter, Vanessa Bennett, was beaten with a hammer in the same fashion as her parents but survived the brutal attack. 

Ewing was connected to the case through DNA evidence. He emerged as a suspect in 2018 while he was serving a 40-year prison sentence in Nevada for attacking a Las Vegas-area couple with an ax handle in 1984 in their bedroom. 

He was extradited to Colorado to stand trial. 

"When we first looked at it, we thought that it was likely that the killer was long gone," said Eighteenth Judicial District Attorney John Kellner, the Denver Post reported. "And we didn’t have much hope then. But science and progress keeps marching on."

Ewing’s attorneys argued that the prosecution's evidence in the Aurora case had been tainted over the decades.

Public defender Stephen McCrohan also told jurors that evidence from the Bennetts' home pointed to people other than Ewing being responsible. He faulted investigators for working without gloves and not properly securing the crime scene at the home after the killings.

Constance Bennett, the mother of murder victim Bruce Bennett, is questioned by District Attorney John Kellner during Alex Ewing's murder trial. (Philip B. Poston/Sentinel Colorado via AP, Pool)

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Prosecutors said Ewing lived two blocks away from the Bennett home. He is also suspected of killing a 28-year-old Aurora woman, 50-year-old Patricia Louise Smith and beating another couple in Aurora, Fox 31 Denver reported. 

Ewing is scheduled to stand trial in the death of Smith in October. He faces life in prison when he is sentenced later this month. 

Bruce Bennett's mother, Connie Bennett, 87, testified that she discovered her son's bloody body inside the home after her son and his wife did not show up for work.

"A weight was lifted off today," she said after the verdict. "We’ve been waiting a long time for this." 

The Associated Press contributed to this report.