From the PI.com:

The man who police say flipped his car on Aurora Avenue North killing his passenger during an early morning wreck Monday is being held for investigation of vehicular homicide.

However, prosecutors are not likely to file charges by the Wednesday rush deadline. Seattle police is still investigating collision-reconstruction evidence.

"And we are awaiting lab results to either confirm or eliminate the possibility of any influencing substances in the suspect's system," said Ian Goodhew, deputy chief of staff for King County Prosecutor Dan Satterberg.

Seattlepi.com is not naming the driver because he hasn't been charged. The passenger who died was identified Tuesday by the King County Medical Examiner's Office as Jamal Michael Clayton, 23.