NORTHAMPTON — A Westfield man pleaded not guilty Tuesday morning to charges of manslaughter and tampering with evidence for his alleged role in the overdose death of a South Hadley woman in May.

Christopher Halla, 42, allegedly sold the 57-year-old woman a drug that he claimed was oxycodone, according to the Northwestern district attorney’s office.

In reality, the drug contained metonitazene, a synthetic opioid that prosecutor Joseph Webber said can be “up to 10 times more potent than fentanyl.”

The woman was found dead on May 23, and the primary cause of death determined by a toxicology report was metonitazene overdose, Webber, an assistant district attorney, said during Halla’s arraignment in Hampshire Superior Court.

This is the first manslaughter charge in the Northwestern district brought due to fatal drug overdose since the Supreme Court’s 2019 Carillo decision, according to the DA’s office. In the Carillo decision, a University of Massachusetts graduate student was convicted of selling a fatal dose of heroin to an undergraduate student, but the court held that selling heroin to someone is not reckless or dangerous enough to warrant a manslaughter conviction.

This case differs in that, rather than heroin, the defendant is alleged to have sold pills to the victim containing metonitazene, the DA’s office said in a statement.

At the arraignment, Webber said that Halla had obtained the victim’s phone number through a friend, and offered to sell drugs to her. The victim, who suffered from chronic pain, believed that the pills would provide some relief, but had not been actively seeking them. Webber asserted that Halla “repeatedly misled the victim” about the pills, and “repeatedly assured her that they were legitimate oxycodone” and that they were “safe.”

Webber also said that Halla was selling these pills for $30 each, and sold 30, worth a total of $900, to the victim.

Halla also allegedly tampered with evidence after being arrested on May 28, following the victim’s death. Upon being arrested, Webber said Halla called his girlfriend and asked her to flush the pills that were stored at her residence.

Halla’s appointed defense attorney, Michael Sheridan, said that because several people live at this Turners Falls residence and Halla did not specify that the pills were his, it is not certain that Halla was asking for his own stash to be flushed — rather he was issuing a “warning.” Sheridan maintained that Halla had been compliant throughout the whole investigative process.

Sheridan said Halla is currently homeless and unemployed, and living in a tent in the Greenfield area. During the arraignment, Halla remained silent throughout with his gaze fixed directly forward or cast downward.

On behalf of the commonwealth, Webber requested that Halla’s bail be set at $100,000 to “ensure his appearance,” citing previous failures to appear at the district court level, as well as a past of criminal behavior including two past counts of disobeying a restraining order.

Sheridan contended that because of Halla’s circumstances, he would be unable to pay bail at that level, and suggested that he be given a GPS tracker instead.

Judge Bertha Josephson maintained that bail should be set at $100,000 due to Halla’s past, the nature of the charges and his insufficient community ties, even though she acknowledged he would be unable to pay this amount. The bail was set without prejudice, and may be reconsidered at a later date.

In a statement, Northwestern District Attorney David Sullivan acknowledged that bringing a manslaughter charge in this case is unusual, but held that it is appropriate given the circumstances. He stated that when prosecution is warranted, it must be pursued “to save lives amid our country’s overdose death epidemic.”

“I also support judicious use of this office’s prosecutorial authority as we continue to battle with the scourge of counterfeit, lethal pills endangering the lives of so many in our community,” Sullivan said.

Halla faces other related charges as well. As part of the investigation into the victim’s death in this case, the State Police Detective Unit assigned to the DA’s office and the DA’s Anti-Crime Task Force used an undercover police officer to conduct a controlled purchase from Halla, resulting in the seizure of more metonitazene pills. Related to that incident, Halla was indicted by a Franklin County grand jury for possession with intent to distribute a class A substance.

Additionally, when Halla was arrested on May 28, he allegedly had heroin in his pocket. According to Webber, Halla was arraigned in the Hampshire County District Court following his Superior Court appearance with a misdemeanor count for possession.

Halla’s pre-trial hearing in the Hampshire County Superior Court for counts of manslaughter and tampering with evidence will be on Jan. 21 at 2 p.m.

Alexa Lewis can be reached at alewis@gazettenet.com.