A man stabbed his girlfriend 15 times before jumping eight metres (25ft) out of a second-floor window on to a car and attacking passersby, a court has heard.

Michael Marler, 37, admitted manslaughter at a previous hearing but denies murdering his 24-year-old girlfriend, Danielle Richardson, in Manchester on the night of 12 February this year.

Marler told police that he had taken a large amount of crack cocaine that night and that – although he was used to taking the drug – this time it had an unusual effect on him. He said he has no memory of killing Richardson.

Richardson was found on the floor of a central Manchester flat, face down and covered in blood. She had been stabbed in the face and neck and had received 11 stab wounds to her back. A paramedic who attended the scene found no signs of life.

The Oldham couple, who had been in an on-off relationship for three years, had been renting the apartment in the Ancoats area of the city while Richardson’s flat in Oldham was being redecorated.

The jury at Manchester crown court was shown CCTV of the pair arriving at the Shush Apartments, Swan Street at around 6pm before going out to the cinema. Marler told police that he and Richardson bought crack cocaine that evening after going on a “drugs spree” in the preceding weeks.

“By 8am the following morning, Miss Richardson was dead. She had been stabbed 15 times with a knife. The person who stabbed her was the defendant,” said Neil Usher, opening the case for the prosecution.

“He has admitted stabbing her to death at a previous hearing. We, the prosecution, say that Danielle Richardson was murdered by this defendant.”

He said that the jury would have to decide whether Marler intended to kill or cause her serious bodily harm to Richardson.

CCTV footage shown to the jury dating from around 7.30am on the morning of 13 February depicted the defendant jumping eight metres from the window on to the roof of a car that had pulled up outside the apartment block. Marler could be seen wrestling with Peter Sheridan, who had just got out of the car, as the defendant made an apparent attempt to get into the driver’s seat.

Giving evidence on Tuesday, Sheridan said: “When I saw legs [on top of the car], I thought it was a body and that someone was dead, but then he was moving. I helped him up because I didn’t know what had happened. There was lots of blood everywhere, which I assumed was his.” He described the defendant’s face as being blank.

Marler then ran off and footage taken on a mobile phone shows him, with blood on his arms, wandering between cars on the roads during rush hour. Witnesses described him punching cars and biting a pedestrian. While attempting to detain Marler, police heard the defendant say: “I’m dead, I’m dead, she’s dead.”

After gaining entry to the flat, officers saw blood on the walls and floor before finding Richardson’s body.

The cause of death was determined to be multiple stab wounds and the court was told that Home Office pathologist Dr Philip Lumb concluded that severe force must have been used to cause the injuries.

“In some of the injuries, thick sections of hard bone had been cut into, which requires a high level of force,” said Usher.

The trial is expected to last seven days.