A New London judge ruled Friday that Chad M. Schaffer, who pleaded guilty to partaking in the 2004 beating death of physicist Eugene Mallove in Norwich, cannot be compelled to testify at the murder trial of his cousin and co-defendant Mozzelle Brown.

Judge Barbara Bailey Jongbloed’s ruling means the state will have to rely on Schaffer’s ex-girlfriend, Candace Foster, for first-hand testimony in the case. Foster’s credibility has been called into question in previous court proceedings, during which she admitted she repeatedly lied during the investigation of Mallove’s death.

Jongbloed’s ruling came after Schaffer, led into court by correction officers, took the witness stand, exchanged glances with Brown at the defense table and repeatedly responded, “I take the Fifth (Amendment)” to questions posed by prosecutor Paul J. Narducci.

Schaffer, a pizza cook who was charged with Mallove’s murder in 2010, accepted the state’s offer to plead guilty to the lesser charge of manslaughter in the middle of his 2012 trial in exchange for a sentence of 16 years in prison. Now 37, he is incarcerated at the MacDougall-Walker Correctional Institution.

Subpoenaed recently by the state to testify at Brown’s trial, his attorney, Joseph A. Jaumann, filed a motion to quash it, claiming his potentially self-incriminating testimony could hurt him in a habeas corpus appeal he has filed.

Narducci and Jaumann both cited existing case law in arguing their positions, but the judge noted this was “a unique issue.”

“It’s a very high standard to deny a witness his right to invoke his Fifth Amendment right,” Jongbloed said. She said the ruling was not a “blanket statement,” but that under the circumstances, she was granting the motion to quash.

Narducci had argued that the invocation of Fifth Amendment rights is valid when the witness has taken a direct appeal, but that Schaffer pleaded guilty and has a pending habeas corpus lawsuit, not a direct appeal.

“If one could assert their privilege when a habeas corpus is pending, in essence that person is protecting himself almost ad infinitum,” Narducci said.

Prisoners can file an unlimited number of habeas corpus claims, which are sometimes called the appeal of last resort. They bring the lawsuits against the Department of Correction, claiming they are wrongfully incarcerated. Schaffer claims in his habeas corpus appeal that he had ineffective legal representation and that he is innocent of the crime.

Though they may be called on to testify later in the trial, Schaffer’s parents, Pat and Roy Anderson, who had been evicted from Mallove’s rental home at 119 Salem Turnpike in the months before his death, were allowed in the courtroom for the hearing.

The state alleges Brown and Schaffer attacked Mallove because he was throwing out items that belonged to the Andersons. They allegedly left Mallove injured and lying in the driveway and returned with Foster and forced her to participate in the continued assault on Mallove, who pleaded for help.

Foster, who also is incarcerated on murder charges, is cooperating with the state and is expected to testify early next week.

k.florin@theday.com

Twitter: @KFLORIN