The CHP says Tran was under the influence of marijuana when he crashed into a family on Interstate 880 near Stevenson Boulevard Tuesday.
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Once someone is arrested and booked, prosecutors have 72 hours to file charges. That deadline was up so the suspect had to be released from jail.
The Alameda County District Attorney's Office released a statement saying: "The investigation in this matter is ongoing and the DA's Office requires additional information as well as investigation prior to making a charging decision."
Former prosecutor Steven Clark explained what may be missing. "Marijuana requires a detailed blood test and it's likely that the DA has not received the toxicology report from the crime lab yet."
Marijuana cases are not as straightforward as alcohol. There's no court-approved test yet like a breathalyzer for alcohol.
There's also no legal limit established like the .08 for alcohol.
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Toxicology reports will be paired with field sobriety tests and officer observations.
The central focus will be whether he was impared by marijuana at the time he was driving.
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