Nelson was a "doctor-shopper," Shaver said, seeking painkillers and anti-anxiety drugs from different physicians.
A state Justice Department toxicologist said he found "high" amounts of oxycodone, the painkiller, and evidence of recent marijuana use after testing Nelson's blood after the crash that killed Michael Richey, 46, on a rural road east of Modesto on Sept. 30, 2008.
"The defendant knew about the danger and acted with conscious disregard for human life," Deputy District Attorney Nate Baker said.
Defense attorney Mary Lynn Belsher said Nelson should be charged with vehicular manslaughter — meaning an accidental killing, as is typical in DUI fatalities — not the more severe charge of murder.
The distinction could mean life in prison for a murder conviction compared with as little as probation for manslaughter.
"Mr. Nelson and I are sorry Mr. Richey is dead ... but that doesn't make Mr. Nelson a murderer," Belsher said. "There's no science to support the position that oxycodone actually affected my client's ability to drive."
The Justice Department toxicologist agreed, saying there were no studies that looked at oxycodone's effect on driving ability.
But authorities said Nelson performed badly on a field sobriety test. And a witness driving behind Nelson on Milnes Road said Nelson weaved from shoulder to shoulder, running a stop sign before he hit Richey from behind on the two-lane road.
"There's ample evidence ... that (Nelson) was acting like he was under the influence," Shaver said.
The judge said Nelson also will stand trial in another DUI crash, also involving a bicyclist. Nelson is accused of injuring a boy riding his bicycle across a Modesto street in March 2008, just six months before Richey's death.
Nelson also was charged with a misdemeanor: driving on a suspended license.
He will be back in court Dec. 17 to be formally charged in connection with that crash.
Nelson remains in jail in lieu of $1 million bail.
Bee staff writer Merrill Balassone can be reached at mbalassone@modbee.com or 578-2337.