SCOTTSDALE, Ariz. - The Scottsdale Police Department has arrested a suspect in the murder of Allison Feldman.

Feldman, a 2001 graduate of Minnetonka High School, was found dead in her Scottsdale home in 2015. She had been working in sales for a healthcare company in Scottsdale.

"We have collected close to over 450 items of evidence, interviewed well over 300 people. We never stopped investigating. This was never a cold case," said one law enforcement official on Tuesday.

A 42-year-old man from Tempe is in custody pending first-degree murder charges.

"When I found out last night police were about to make an arrest, it was shocking to say the least. I don’t know if I can use the word relieved yet, but we have been wanting a long time. Obviously, I don’t think we will ever know the why, but at least knowing the who helps answer some questions," said Kelly Weinblatt, Allison's sister, who lives in the Twin Cities.

Investigators with the Scottsdale Police Department and Arizona Department of Public Safety used familial DNA to make the arrest. Arizona is one of 12 states in the nation that can perform familial crime lab testing. Minnesota and Wisconsin also have access to the same technology.

How did it happen? The Scottsdale PD gathered an unknown DNA sample from the crime scene. It was then compared to the state database. When no match was found, police asked the Arizona Department of Public Safety to conduct a strenuous familial DNA test. Years later, a family link was established and investigators were able to identify a family member in the justice system. Investigators then questioned that family member's sibling and made Tuesday's arrest.

"It's probably one of the biggest advancements in our lifetimes. With this technology, we can bring years of frustration to an end," DPS Director Frank Milstead said.

"If it can help another family get an answer to who, that is a wonderful legacy for her," said Weinblatt.

No direct known link between Feldman and the suspect has been made. The suspect also does not have a history of violent crime.

Stay with KARE 11 for more on this developing story.