SEATTLE -- A man who pleaded guilty to stabbing his girlfriend to death as they rode in a car on Interstate 5 in Seattle was sentenced Friday.

Kristell Murphy was in the back seat of a car on I-5 in North Seattle in October 2008 when he reached into the front passenger seat and stabbed his then girlfriend, Jane Kariuki, 32 times.

Kariuki’s mother, Rosemary Kariuki, told the judge she wanted Murphy to be sentenced to 64 years in prison -- two years for each of her daughter's 32 stab wounds.

When it was his turn to speak, Murphy apologized to Kariuki's family and to his own. He told the judge he didn't know why he did what he did.

In the end, the judge imposed a sentence at the top of the range, nearly 30 years in prison.

Afterwards, Kariuki's sister had a warning for women involved in abusive relationships.

“I just want to tell people just get out -- don't be afraid, get out, there's help out there," said Ann Kariuki.

She said she would have preferred a stiffer sentence.