LANCASTER — A Berlin man has pleaded guilty to selling the dose of fentanyl that earlier this year killed a father of three from Whitefield.

Jonathan Duff, 30, formerly of Hillsboro Street, appeared Wednesday in Coos County Superior Court before Justice Peter Bornstein and waived indictment on one count of distribution of drugs, death resulting, for knowingly dispensing or selling fentanyl on Feb. 3 to Adam L. Warren.

Duff also pleaded guilty to two other felonies: possessing fentanyl with intent to distribute and being a habitual offender.

On the first charge, Bornstein sentenced Duff to serve between 10 and 20 years in New Hampshire State Prison; gave him 265 days of pre-trial credit; and deferred two years of the minimum sentence conditioned upon good behavior. Duff also must pay $3,496 towards the cost of Warren’s funeral.

On the possession charge, Bornstein sentenced Duff to between 7.5 and 15 years in prison, all suspended for 15 years. He fined Duff $1,000, also suspended for 15 years and ordered him to give back $100 in “buy money” to the Berlin Police Department.

Duff waived indictment on the habitual offender charge and was sentenced to between one and four years in prison, which he will serve concurrently to the death resulting charge. If imposed, Duff’s sentence for possession would run consecutively to the one for death resulting.

“Mr. Duff’s prison sentence should serve as a reminder to those who would sell the dangerous drugs that are plaguing our community — you will be held accountable for your actions, and we are watching,” said Coos County Attorney John McCormick, in a prepared statement. “If you engage in peddling poison, you can expect to go to prison.”

McCormick said the case against Duff was made by the Berlin Police Department and the Attorney General’s Drug Task Force.

According to his obituary, Warren, 36, grew up in Milan and attended Berlin public schools and while working in Berlin, he met Karen Iacoviello, his future wife.

The couple, who married in 2006, have lived in Whitefield since 2003. Warren owned the Climbing Higher Tree Service. He was remembered as a “fun loving guy with a big heart who would do anything for his family.”