Finley says there was DNA evidence found under his wife's fingernails from when she scratched her killer during a struggle.
Police have not ruled her death a homicide.
"I absolutely 100 percent know that this was a murder," Finley said. "I believe it was a rape attempt that went bad because she fought back and somebody ended up breaking her neck."
The Rancho Cucamonga couple was in town so Joe Finley, a singer and guitarist, could audition for the reality show "America's Got Talent."
He said he heard his wife leave their Millennium Biltmore Hotel room about 3 a.m. to go get ice. He fell asleep and when he woke up she wasn't there, but he wasn't alarmed.
"It's not unusual for us not to be together," Finley said. "We can be in any hotel and if she decides she's going to do something, then she does it, or I do it."
Finley went to audition at the show even though his wife hadn't returned. He started to worry after waiting in line for hours. He tried calling and texting his wife to no avail.
When he got back to the hotel, he was met by police detectives who later showed him a graphic photo from the crime scene. Finley said there were strangle marks on his wife's neck.
"Then I collapsed, kissed the picture, dropped to the floor and they took the picture away," he said.
Police did consider Finley a person of interest. The story has gone global, making headlines in London's Daily Mail.
Finley keeps a purple urn with her ashes as part of shrine in her honor. His body is covered in tattoos as a reminder of his wife of 26 years.
Though he doesn't appear to be grieving, Finley said he does that in private because he needs to be strong for his family.
"I'm investigating my wife's murder, I'm protecting our children, my family, her family, everybody's broken down," Finley said. "If I can't stand up, then everybody will fall apart."
Finley is offering a $25,000 reward for information leading to the arrest of his wife's killer.