A Suffolk man pleaded not guilty to second-degree murder Friday in the death of his 17-year-old girlfriend last year.

William Daniel Conroy Jr., 20, also entered not-guilty pleas for charges of distribution of a schedule II drug and contributing to the delinquency of a minor, as well as a charge of arson of an unoccupied building stemming from another incident.

His girlfriend, Briley Marie Compton, went into cardiac arrest in the backyard of his residence, city spokeswoman Debbie George said at the time of his arrest.

Police were told she had fallen from a boat in the backyard, but tests on the body revealed she died because of a combination of Coricidin, an over-the-counter cold medication, and a prescription narcotic, fentanyl, that was not prescribed for her.

“Investigation revealed those items were given to her by her boyfriend,” George said.

The arson charge stems from an incident about three weeks after her death. Police accuse Conroy of burning someone else’s duck blind, George said.

His trial on all the charges is set for Nov. 14-16.