Perry, 22, was diagnosed as schizophrenic, and was being treated in the hospital's psychiatric unit when she was found unresponsive on Feb. 14, 2012.
On Friday, a coroner's jury was shown the videotaped statement the young man gave to police the day after Perry's death.
The young man — whose name is protected by a publication ban — told police that he had gone for a walk through the hospital with Perry and another male patient on the evening of Feb. 14.
He said Perry's mood often changed quickly, but she was talking about God and acting more strange than usual. The young man said he decided to return to his room.
Const. Stephen Davidson, the lead investigator on the case, told the court that the young man was quickly discounted as a suspect, but questioned as a witness.
Security video shown to the jury last week showed Perry and the second male patient leave the psychiatric unit again that evening and head towards the amphitheatre.
Nurses have testified that they couldn't find Perry late that evening, and the second male patient told them he had been with her in the theatre.
That's where they found her, unresponsive, with a blue housecoat around her neck.
A code blue was called. It is an alert indicating there is a patient in need of immediate resuscitation.
In his statement to police, the young man said that when the code blue was heard over the public address system, the other male patient who had been with Perry started to have a panic attack.
The inquest has yet to hear from that patient or see the videotaped statement he gave to police.
Outside the court, John Gillis, the lawyer for the Perry family, said he hopes the patient is called to testify.
"I think it would be important for the jurors because they are tasked with finding out what happened to her," Gillis said. "I think that's crucial and I hope we hear from him or at least hear from his statement."
Earlier Friday, two nurses who found Serena Perry in the amphitheatre were recalled to comment on the housecoat found around Perry's neck.
A picture shown to the coroner's jury of a re-enactment of the scene in the amphitheatre included a mannequin with a housecoat tied around its neck.
Melissa Schima and Paula Murphy said there was no knot and the robe was loose around Perry's neck.
Schima, who performed CPR on Perry, said the housecoat wasn't tight enough to choke somebody.
The jury also watched the videotaped statements both women gave to police the day after Perry was found.
Outside the coroner's court, Perry's mother wept and said it was difficult to hear those statements again.
"It brought me back to the same day when I found out that she died. This is hard because she's my baby," said Rose Perry.
Efforts to resuscitate Perry failed.
Two pathologists identified asphyxia due to strangulation as a probable cause of death for Perry, but they didn't have enough information to make a conclusive determination about how she died.
No charges have been laid.
The five-member coroner's jury will make recommendations to help prevent similar deaths in the future.
The inquest will begin its third week on Monday.