BUFFALO - 15 years after her mother disappeared, a young woman watched as her father was sentenced to prison Monday.

Susan Waller helped put her father behind bars.

"We were always abused physically, and there were times when I was younger that I thought he had killed her."

In 1992, her parents Robert and Janet Kirkup, took a cross-country road trip. The Michigan couple stopped in western New York. That's when Janet disappeared.

"He let my sisters and I know that my mother left with another man, and that she didn't want to be a mother anymore."

Kirkup told investigators the same story. His youngest daughter Susan never believed it.

When her father eventually settled in Big River California in the late 90s, Susan pleaded for detectives to re-open her mother's case.

In June, authorities finally listened. Robert Kirkup confessed to strangling his wife while on a camping trip in Genesee County.

After enjoying 68 years of freedom, Kirkup was extradited to New York.

A judge sentenced him Monday to five to 15 years in prison for manslaughter.

Capt. John Hibsch from New York State Police said, "Hopefully one day we'll be able to put some closure or additional closure to the family."

The prosecution didn't push for murder because investigators haven't found Janet's body.

State Police aren't giving up their search, focusing in Darien Lake State Park and the former Indian Falls State Park.

Susan Waller isn't giving up either.

"My only focus is to find my mother's remains so I can give her a proper burial and put her to rest."