STEUBENVILLE, Ohio (AP) - A computer expert has begun testifying about analyzing cellphones seized in the investigation of two Ohio high school football players charged with raping a 16-year-old West Virginia girl.

The evidence to be presented by computer forensic specialist Joann Gibb is considered crucial to prosecutors' case against the boys because of cellphone pictures taken the evening of the alleged attack in August.

The questioning of Gibb by prosecutors and defense attorneys is expected to last several hours Thursday at the trial in Steubenville in eastern Ohio.

Text messages and social media messages led to authorities being told of the alleged attack.

Attorneys for the two boys argue they're innocent. The teens could be imprisoned until their 21st birthday if found guilty of rape.