Three local high schools are among 16 schools that were named regional finalists for the Massachusetts Bar Association's Mock Trial Program .
Teams from Chelmsford, Marblehead, and Winthrop earned titles by competing in regional trials in January and February.
About 130 high schools signed on for initial participation in the 28th year of the program.
The mock trial program aims to increase student understanding of the legal system, strengthen advocacy and communication skills, and create an opportunity for young people to learn about law-related professions, according to the bar association.
The program consists of realistic role-playing of legal battles where students assume the roles of courtroom participants: plaintiff attorneys, defense attorneys, and witnesses.
This year's "case" involves the prosecution accusing the defendant of poisoning and killing his great-aunt. The defense alleges that she died of natural causes or that someone else murdered her.
After this week's round, the 16 finalists will be cut down to eight teams that will face off for spots in the state semifinals, and then four teams will compete during trials to be held in Boston and Worcester on March 18.
The final two contending teams will fight for the state championship in the Great Hall of Faneuil Hall in Boston on March 20.
State winners go on to the National High School Mock Trial Championship, which will be held May 9 through 11 in Indianapolis.
Chelmsford won the state title in 2003.
Pioneer Valley Performing Arts Charter Public School of South Hadley, one of this year's 16 regional contenders, won the state championship in 2011 and 2012.