The victim, identified as Jane Kariuki, 42, was sitting in the front passenger seat at the time of the attack. Her brother-in-law was driving and her boyfriend was in the backseat.
According to court documents, Kariuki and the man had been arguing for most of the day. As they headed south on I-5 during rush hour, Kariuki told the man she wanted him to move out. That, prosecutors say, is when he grabbed her in a headlock and stabbed her.
The driver pulled over at North 92nd Street and called 911.
The boyfriend got out of the vehicle, tossed his knife on the ground, lit a cigarette and leaned up against a guardrail until police arrived, court documents say.
Kariuki's brother-in-law performed CPR on her, but she died from her injuries at Harborview Medical Center.
According to court documents, the couple had been together for the past five years in what was a volatile relationship.
In 2006, the man was sentenced to 60 days in jail for third-degree assault and ordered to complete counseling for domestic violence batterers.
In that case, officers found Kariuki at the couple's apartment in the 2300 block of 56th Place South bleeding from her right ear and fingers.
The woman told officers that the fight that day began when the boyfriend accused Kariuki of "monopolizing" the television and not paying him attention, court documents say.
Kariuki pulled her car key from his key ring to prevent him from disabling her car, she said. But the act infuriated the boyfriend, who punched her several times and deliberately broke a glass and cut her fingers with one of the shards.
She told the officers he warned her that if she called police, she would be "way gone before they got here."
Kariuki locked herself in a bathroom and called 911, but the boyfriend had fled before police arrived.
Kent police arrested him a few days later at his work.
They noted that they had gone to the home 10 days earlier for another domestic violence episode, court documents say.
By October 2006, the boyfriend had completed his jail term over the attack, and he and Kariuki asked the court to lift a no-contact order between them.
Initially, Judge George Mattson denied the request. But five months later, the judge agreed to rescind the order after seeing evidence that the boyfriend had undergone domestic violence batterers' counseling.
Then, in July 2007, the man was charged in Kent Municipal Court in another episode involving Kariuki, prompting another order to take effect.
The man who police say stabbed his girlfriend to death on Interstate 5 last week was charged Monday with first-degree domestic violence murder.
Christel D. Murphy, 42, was in a Suzuki Grand Vitari when he put her in a neck hold and stabbed her 31 times, cutting her neck face and chest, according to court documents.
After stabbing 42-year-old Jane Kariuki – a woman he had abused and threatened to kill before in their five-year relationship – police say he threw the knife on the road, leaned against a guardrail and lit a cigarette.
Murphy pled guilty to fourth-degree assault against Kariuki in July 2007. He was also charged with third degree-assault and harassment for a March 2006 incident after he hit Karuiki in the head, threatened her with a knife and cut her hand with a glass shard.
When the woman threatened to call police, Murphy said she would be "way gone before they got there," according to court documents.
Murphy remains in King County Jail on $4 million bail.