Prosecutors intended to use Derhammer's lack of inquiry about his former girlfriend, Nancy Kostelnick, 48, and her daughter, Carolyn “CJ” Kostelnick, 23, when he was questioned by city police on April 13, 2009.
The mother and daughter died from smoke inhalation due to a fire at their house at 46 Chester St., Wilkes-Barre.
Police and county detectives allege Derhammer set the fire on a rear porch because he was angry Nancy Kostelnick had thrown him out two weeks earlier. He is facing two counts of criminal homicide, one count of criminal attempt to commit homicide and four counts of arson.
Judge Joseph Sklarosky Jr. on Tuesday granted a request by Derhammer's attorneys, Thomas Marsilio and William Watt, to prevent prosecutors from introducing testimony about Derhammer's silence about the welfare of Nancy and Carolyn Kostelnick.
City police Detective Ronald Foy questioned Derhammer the day of the deadly blaze.
“During this entire process, including the interaction with Derhammer at the scene, during his transport, and while he was waiting, he never asked what happened at the house or if Nancy, CJ or Joe (Kostelnick) were alright,” according to Foy's report.
Joe Kostelnick was Nancy's husband, but he allowed Derhammer to stay at the Chester Street house that has since been demolished.
Assistant District Attorney Mary Hanlon Mirabito argued Derhammer's lack of inquiry about the women's welfare is relevant to his guilt. Watt countered that Derhammer's right to remain silent is being used by prosecutors unlawfully.
Prosecutors filed an appeal Tuesday afternoon with the state Superior Court.
The appeal will likely continue Derhammer's trial, scheduled to begin Monday.
In an unrelated case, Derhammer was convicted of failing to comply with registration requirements under the state's Megan's Law after a bench trial presided over by then-Judge Lewis Wetzel on March 3, 2011. He was sentenced to 40 to 80 months in state prison on April 20, 2011.