The Cape and Islands district attorney’s office has declined to prosecute an Edgartown man for manslaughter in an unusual case that involved a private complaint following a fatal drug overdose in Vineyard Haven last April.

Aaron R. Bezahler, 22, was scheduled to be arraigned Thursday in Edgartown district court on one count of manslaughter after the mother of an overdose victim alleged that he sold her son the drugs that killed him.

But in court on Thursday morning, Cape and Islands assistant district attorney Ben Vaneria told Judge James J. McGovern that the commonwealth was filing a nolle prosequi prior to arraignment. Nolle prosequi means the commonwealth does not intend to prosecute the case and effectively dismisses the charges. In this case, the commonwealth said it would not be able to meet its burden of proof and the complaint was defective as a matter of law.

The entire proceeding was over in a few minutes, and Mr. Bezahler left the courtroom, accompanied by family members.

The case centered on the death of Antone Silvia, who was 26 when he died of a fatal overdose in Vineyard Haven on April 20. According to an autopsy report filed in court, the cause of death was acute fentanyl and ethanol intoxication. After a police investigation, Mr. Bezahler was arraigned in June on charges of conspiracy to violate drug law and distributing a class A drug (heroin). Police said cell phone information, text messages and other information showed that Mr. Bezahler allegedly helped Mr. Silvia buy heroin shortly before his death.

The case is slated for trial this spring.

Meanwhile, last month Mr. Silvia’s mother, Brenda L. Williston-Floyd of Fairhaven, filed an application for criminal complaint seeking a charge of manslaughter against Mr. Bezahler. In a letter filed in court, Ms. Williston-Floyd claimed Mr. Bezahler’s negligence led to her son’s death because he allegedly sold him heroin laced with fentanyl, a more potent drug, without her son’s knowledge. “So by Antone thinking he was taking heroin, he gave himself a dosage that he knew he could handle,” she wrote. “Since what he was given was fentanyl it ended up being a lethal dose.”

“Mr. Bezahler’s negligence has affected our family greatly and [Mr. Silvia’s] son has to go on without his dad being by his side,” the letter concluded.

Sitting in for Edgartown district court clerk-magistrate Liza Williamson, who recused herself from the matter, Barnstable court clerk magistrate Charles J. Ardito 3rd found probable cause for the charge.

But the matter ended Thursday when attorneys for the commonwealth said they would not prosecute.

“Even if the language of the complaint comported with the law, the evidence in this case would not permit the commonwealth to meet its burden of proof with respect to the crime of manslaughter,” a nolle prosequi motion filed by the commonwealth said in part.

Parties in the case have agreed to a March 19 trial date for Mr. Bezahler’s drug charges.