A manslaughter case involving a fatal overdose from the powerful drug fentanyl has been moved from Dukes County superior court to Barnstable, after a motion was allowed by a superior court judge last week.

Among other things, the attorney for Jason R. Willoughby, 34, of Vineyard Haven, had argued that it would be difficult to find an impartial jury.

The case dates to 2018, when the defendant was charged with involuntary manslaughter in the overdose death of an Island woman, as well as distribution of a class B substance (fentanyl) and conspiracy to violate drug laws. Mr. Willoughby was indicted by a Dukes County grand jury in October 2018 and arraigned in April. He has pleaded not guilty.

The case will be heard by the Hon. Robert C. Rufo, an associate justice of the superior court who is based in Suffolk County.

Although a trial date of Oct. 9 in Dukes County Superior Court was tentatively set for the case at the time of arraignment, defense attorney Robert Moriarty filed a motion requesting the change of venue, arguing that the case was not ready for trial this October, that several expert witnesses do not reside on the Vineyard, and that the Dukes County Superior Court only sits two months out of the year, making scheduling difficult.

Mr. Moriarty also argued that it would be challenging to select a jury, considering the high-profile nature of both the case and the defendant.

“Obtaining 14 impartial jurors on the Island of Martha’s Vineyard will be a difficult task,” the motion said in part. “The commonwealth’s primary witness and the defendant are well-known on Martha’s Vineyard. This case has received extensive media attention . . . Defense counsel’s last trial in the Dukes Superior Court, which had far less media coverage at the time of the trial, took four court days to seat a jury. Defense counsel suggests that it will take at least six days without summonsing additional jurors, to seat an impartial jury in Dukes County.”

After a hearing, Judge Rufo allowed the motion on Oct. 1. According to Dukes County Superior Court clerk T. George Davis, a Barnstable trial date is expected to be set for sometime in December this year.

According to documents filed in court, Mr. Willoughby allegedly sold his uncle, Leo Willoughby, and his uncle’s girlfriend at the time, Lori Dorsey, a half-gram of fentanyl that led to Ms. Dorsey’s death in February of 2018.

A motion by Mr. Moriarty to suppress evidence obtained from a search of the defendant’s residence was allowed earlier this summer by Judge Rufo. The judge found the police search warrant did not provide a sufficient “nexus” between the defendant’s alleged narcotics distribution activity and his home to support a finding of probable cause, which is necessary for a search warrant.

In August, Judge Rufo also allowed a motion from Mr. Moriarty for further discovery related to Leo Willoughby, ordering the state to produce all entries in the state police database from Sgt. Jeffrey Stone. Mr. Moriarty argues in court documents that Leo Willoughby was used as an informant — but not a registered confidential informant — for the Martha’s Vineyard Drug Task Force.

According to the Center for Disease Control, fentanyl is a controlled substance that is between 50 and 100 times as powerful as morphine.