A police officer says that he initially thought a teenage girl found gang-raped outside a Richmond High School homecoming dance was dead.
The estimated two-week hearing will determine whether there is enough evidence to bring the defendants to trial.
The Contra Costa Times reports that Kaiser said he found the partially nude victim lying underneath a picnic table and covered in vomit in October 2009. When he shook her to see if she was alive, she began moaning.
Kaiser says condom wrappers were scattered on the picnic table.
The seven defendants range in age from 17 to 43. Six of them could face life in prison if convicted.
Investigators say as many as 20 people watched without reporting the crime.