Police have identified 42-year-old Ian Mitcham as the suspect in the case. Police say Mitcham was arrested on Tuesday in Phoenix and was booked into jail for first-degree murder and second-degree burglary.
Through the help of the Arizona Department of Public Safety and familial DNA testing of the suspect's brother in jail on an unrelated charge, detectives were able to track down Mitcham.
"It's probably one of the biggest advancements in my time and [Scottsdale] Chief Rodwell's time in law enforcement," said Col. Frank Milstead of DPS.
Police say they have not connected a single link between Mitcham and Feldman.
In Mitcham's initial court appearance, he denied knowing Feldman and does not why his DNA was inside her house.
"I think the Feldman family as you can imagine, extremely heartbroken, frustrated, but remained very patient," said Scott Popp, Assistant Chief of the Scottsdale Police Department.
"Every discussion we had with them over this three year period I let them know we were going to solve this case. It wasn't a matter of if it was a matter of when."
Feldman, 31 at the time, was found brutally murdered in her home near Loop 101 and Pima Road.
Police said Feldman died of head trauma. According to court documents, she was found nude, and her body smelled of bleach.
In February 2017, Scottsdale police officers canvassed nearby neighborhoods and asked residents for DNA samples. Police were offering a $10,000 reward for information leading to an arrest.
"She'll never come back, and that's what hurts the most," said Harley Feldman, Allison's father. "She was your best friend."
For the Feldman's, this is the next step towards peace, but they'll never get the outcome they really want.
"I don't know if we'll ever get closure. We just miss her a lot. And she'll never come back."
Mitcham's boss told ABC15 that he was a reliable worker and was just as shocked as everyone to learn about the arrest.
"He helped prepare things, he did a lot of stuff, came to work on time," said Mitcham's boss, who didn't want to be identified. "No complaint about him at all."
Mitcham was arrested right outside the deli where he worked for a little more than a year in north Phoenix. His co-workers watched police take him away.
"I can't believe it," said the boss. "It's very unbelievable."
"Thank God this man his behind bars, and our community can feel safe again," said family friend Jazziette Devereaux.
Devereaux organized several vigils for Allison and never gave up hope an arrest would be made.
She now wants to send a message to the suspected killer.
"I wish I could look in this guys eyes, and say, 'You know what? You know those vigils when we said we were going to catch you? You think you got away with this, but you didn't,'" Devereaux said.
ABC15 archive video: Scottsdale woman found murdered in home