SEATTLE - A man who stabbed his girlfriend while they were riding in a car on Interstate 5 near Northgate last October was sentenced Friday to 32 years in prison.

Cristel Murphy, 43, of Kent, pleaded guilty in September to first-degree murder for the stabbing death of Jane Wa Kariuki, 42.

Murphy has a previous manslaughter conviction. His 32-year sentence is near the top of the sentencing range, officials said.

But the victim's sister, Ann Kariuke, said she was hoping for a longer sentence.

"It was a very difficult day, obviously, but we feel that the judge hasn't executed what we hoped for," she said.

According to police reports, Murphy was in the back seat of a car on Oct. 16, 2008, when he grabbed Kariuki, who was in the passenger seat, from behind and stabbed her multiple times.

Kariuki was rushed to Harborview Medical Center where she later died.

Investigators said the pair had been arguing all day and Kariuki had informed Murphy he would have to move out of their home.

According to a police report, Murphy got out of the car after the stabbing, threw the knife on the ground, lit a cigarette and sat on a guard rail along I-5 as police rushed to the scene.

He was taken into custody without further incident.

The incident tied up traffic for hours while investigators processed the crime scene.

Court records show Murphy has a history of domestic violence dating back more than a decade, including two assault convictions for attacking Hariuki. He was also convicted of manslaughter in North Carolina in 1985.