According to prosecutors, Siddoway has a history of seizures and knew he was a danger on the road when he got into his car on Feb. 3, 2013. But he drove anyway, westbound on North Temple, until he had a seizure somewhere between 300 and 400 West in Salt Lake City.
Sarah Kunz was stopped at a traffic light at 400 West in a Nissan Versa when Siddoway's truck careened into her, charging documents state.
Witnesses told police that Siddoway's Ford F-150 continued through the intersection where it also collided with a red Saturn that was stopped eastbound at the light.
Kunz, a passenger in the Versa, later died from her injuries.
Prosecutors allege that Siddoway had been involved in a number of previous crashes caused by his seizures and knew he shouldn't have been driving on that day in February.
The seizures, which allegedly cause Siddoway to lose motor control and be unresponsive for minutes at a time, started in 2009, court documents state. Siddoway told investigators that the "episodes" occurred anywhere from monthly to every six months, even while on medication.
Two years before the fatal collision, Siddoway allegedly suffered a seizure while driving his truck in Coalville. According to court documents, he drove off the road and crashed into the driveway of a nearby home. He fled before police arrived.
In April 2011, Siddoway suffered a seizure at a restaurant.
The next month, he was driving in Provo Canyon when a seizure sent him into the median.
In May 2011, he had a seizure despite being on his medication.
That was the year Siddoway's doctor told him not to drive until he can go two months without an incident.