Mark Baute said the show's creator and executive producer, Marc Cherry, struck Sheridan hard on the head in September 2008 and fired her after ABC cleared him of wrongdoing. Sheridan is seeking roughly $6 million in damages.
Baute said Cherry acknowledges touching Sheridan, but claims he was tapping her head to give her artistic direction.
"This is a man hitting a woman in the head - hard - without her consent," Baute said.
The ABC series' stars, Eva Longoria, Teri Hatcher, Felicity Huffman and Marcia Cross, could provide some star power to the trial because all are listed as potential witnesses. The trial will also provide a behind-the-scenes look at how a major television show is created, with both sides focusing on when the decision was made to kill off Sheridan's character, Edie Britt.
Baute said Sheridan was waging her case mostly alone, but that two of the show's writers will testify that no decision about eliminating Sheridan's character was made until after ABC concluded its inquiry into the slapping incident.
Baute argued that the Edie Britt death was hastily planned and not the result of months of planning as Cherry claims. Britt was killed off in the fifth season.
Attorneys for the show claim it was a creative decision, but the actress said she was wrongfully fired for complaining that Cherry struck her during a fight.
Sheridan dabbed her eyes with a cloth during her attorney's opening remarks, and hugged Baute after he concluded.
Cherry and ABC have denied all wrongdoing. Their defense attorney was expected to make an opening statement later Wednesday.
Jurors will be asked to decide whether Sheridan was wrongfully terminated from the show and whether Cherry committed battery by striking her in the head.
Sheridan and Cherry attended jury selection, which lasted two days. Potential panelists were grilled on whether they had seen the show and their views on television and violence.
"Desperate Housewives," a glossy prime-time comedy/soap opera with an ensemble cast including Hatcher and Longoria, made a pop-culture and ratings splash when it premiered in 2004 but has seen its audience dwindle. It is in its last season.
