Cody Hall, 18, was originally charged with felony vehicular manslaughter in the death of Diana Hersevoort, 58, of Dublin but he was arraigned on murder charges Wednesday, the Bay Area News Group reported Friday.
The newspaper Pleasanton Patch reported Hall boasted on his Twitter account of driving 140 mph on Interstate 5, tweeting "live fast die young" and urging readers to "come on a death ride with me."
Hall was allegedly driving 83 mph at the time of the accident, Bay Area News Group said.
The Twitter message will likely serve as a "pre-offense statement" not unlike an e-mail or handwritten note, to bolster the prosecution's theory of "implied malice" required to prove a murder charge, said Brian Welch of the Santa Clara County District Attorney's office.
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