Speed initially was arrested on suspicion of automobile homicide, hit and run and driving under the influence.
West Valley City police Sgt. Jason Hauer said investigators formally screened the case with the district attorney's office, which declined to file charges.
The case was then referred to West Valley City prosecutors, who filed a class B misdemeanor of driving under the influence in the city's justice court against Speed.
Speed has pleaded not guilty to the DUI charge. His attorney could not immediately be reached for comment Tuesday.
Charging documents obtained by The Salt Lake Tribune through an open records request show that when officers interacted with Speed, he had difficulty following simple instructions and his speech was unusually fast and incoherent.
"He admitted to drinking two or three beers and stated that he is a frequent methamphetamine user," the investigator wrote in his probable cause statement in the charging documents.
The officer noted that police had to obtain a warrant to draw Speed's blood because he refused a sobriety test, telling officers his blood would test positive for methamphetamine.
Brad DeBry, who has been retained to represent the Chase family, said he was baffled to learn Speed won't face automobile homicide charges. He equated the misdemeanor DUI charge, which carries a maximum punishment of up to six months in jail, to a "slap [on] his hand."
"Are you kidding me?" DeBry asked. "The guy is drunk and he kills someone. That they think he wasn't negligent bothers me."
Gill said his office declined to file the case because Speed's alleged actions did not rise to the level of negligence required to pursue an automobile homicide charge.
In addition to being intoxicated, a defendant needs to be doing something else negligent behind the wheel like speeding or swerving in and out of traffic or driving without lights, Gill said. He said the investigation determined Speed was not doing any of those things at the time of the crash. Court records do not indicate what Speed's blood-alcohol level was at the time of the crash.
"It's not simply being intoxicated," Gill said. "It's being intoxicated and criminally negligent."
In addition, Gill said Chase was jaywalking late at night while wearing dark clothes across a busy roadway, so it would have been difficult for prosecutors to prove that a sober person would not have struck Chase.
DeBry said most sober people likely would have avoided striking Chase by slowing down or swerving.
"You're not supposed to be jaywalking, but you're not supposed to be killed because of it," DeBry said.