HALIFAX -- Police detected DNA matching the genetic profile of Taylor Samson on a gun and a bullet found in the Halifax apartment rented by the medical student accused of killing him in the midst of a drug deal, a Crown attorney said Thursday in her dramatic opening address to William Sandeson's murder trial.

Crown lawyer Susan MacKay said the gun was found after police made an emergency entrance into the apartment "because they were concerned that Mr. Samson was being held hostage there" -- this after police read text messages between the two Dalhousie University students.

"Forensic examination of the scene revealed several places that looked like blood, or blood that had been cleaned up," MacKay told the jury in Nova Scotia Supreme Court.

"DNA with the profile matching Taylor Samson's was found on the gun. Police also located a bullet lodged in the window casing in the kitchen. The bullet was tested for DNA, and DNA with a profile consistent with Taylor Samson's DNA profile was found on that, too."

Sandeson, 24, was charged with first-degree murder on Aug. 20, 2015, four days after Samson, a 22-year-old physics student, was reported missing. His body has yet to be found.

On the night he was killed, Samson left his fraternity house on South Street in Halifax, telling his girlfriend he would not be long -- but he never returned, MacKay said.

"Although, for obvious reasons, (his girlfriend) at first was reluctant to tell police about Taylor having been involved in drug dealing, once police realized that he was, this increased their level of concern about his disappearance," MacKay said.

The last time Samson was seen alive, MacKay said, he was recorded on a surveillance video walking into Sandeson's apartment to sell 20 pounds of marijuana to the accused for $40,000.

"You will see a video showing the accused walking ahead of Taylor Samson toward the apartment door," MacKay told the jury. "Taylor Samson is carrying what looks like a bulky hockey-style black duffle bag."

MacKay said Sandeson had set up three, motion-activated video cameras that captured images from the adjacent staircase, hallway and from outside the building.

Although police never found Samson's cellphone, investigators were able to obtain the last phone number he dialled on the night he disappeared, MacKay said. That number led investigators to Sandeson.

When police tried to contact Sandeson, the accused first went to his apartment, where he removed garbage bags and other items -- actions all captured by his video cameras, court heard.

"Later examination of the (video) contents shows him walking with these things through the hallway and outside his apartment while wearing coloured gloves," MacKay said.

During a police interview, Sandeson described different versions of his encounter with Samson, the lawyer said.

She said data taken from cellphone towers showed Sandeson's phone was in the Truro area later that night, where his family has a farm.

"A later search of this property by police, following (Sandeson's) arrest, turned up items matching the description of what William Sandeson was seen removing from his apartment," MacKay said.

Court heard police also recovered a shower curtain and a pair of gloves resembling the ones from the video.

"They also found a large, black, hockey-style duffle bag with a ripped shoulder strap," MacKay said. "DNA found at the scene contained the profile that matched the DNA profile of Taylor Samson."

Later in the day, Samson's mother wept as MacKay showed her a photo of her son.

Under cross examination, Linda Boutilier said she was aware her son was selling drugs, but she had thought it was small amounts.

The accused, who is originally from Truro, N.S., and is a former varsity track athlete, sat at his lawyers' table throughout the proceedings, occasionally referring to a laptop computer and documents spread out in front of him.

The trial is scheduled to resume Monday and is expected to take 32 court days.