He told the court he pulled over and walked to the parked vehicle.
"There was a person lying, their seat was reclined a bit," Mr Ali said. "I could see a little bit of blood on the person. It was on his shirt and around his face area."
He said Kaur was shaking the man "as though to wake him up" and after asking her what happened several times in Hindi, she responded.
"She said that he was talking to somebody and that person took his phone and stabbed him," Mr Ali said.
Crown prosecutor Natalie Walker in her opening suggested that had been a story concocted by the defendants to make the attack look like a robbery gone wrong.
Mr Ali called emergency services and was told over the phone to check whether Davender Singh was breathing but struggled to do so because of Kaur's position inside the car.
"She had her face over his face and she was crying over him," he said.
He told the call taker there was a "flap of skin" across the man's neck, where it had been sliced, and he was told to apply pressure.
He passed the message on to the victim's wife who he said grabbed a scarf from the back to push against the wound.
The Crown allege Amandeep Kaur and Gurjinder Singh had begun an affair months before Davender Singh was killed in August last year.
After 130 calls and more than 1000 text messages in the space of three months, it is alleged their respective partners discovered the relationship and electronic communication between the couple ceased.
But Ms Walker said their contact continued in the form of hand-written notes.
The Crown said the plan to murder Davender Singh was clearly apparent through those letters, which were allegedly found by police after the killing.
Yesterday the court also heard a knife - exhibited in court in a plastic box - was foun wrapped in a towel and some bloody clothes under a plastic sheet in Gurjinder Singh's
garage.
Forensic testing allegedly found both his DNA and that of the victim on the weapon, it is alleged.
Earlier today the court also heard from the victim's cousin Narender Dhounsi, who had been living with the couple.
He described their relationship as "very good" and said the only disagreements they had were the type common in all marriages.
The trial, before Justice Graham Lang and a jury of nine men and three woman, is scheduled to last four weeks.