A Mercedes driver accused of running a red light and smashing into another car, killing two mothers, was allegedly seen laughing on the phone shortly after being interviewed by police, a court has heard.

Mohamad Hassan​, a 20-year-old Lebanese citizen, had been in Australia for a year when the unregistered black Mercedes he was driving sped through a red light on Sunday night and slammed into a Toyota, killing its two occupants, a court was told on Tuesday.

The speedometer needle on Hassan's car was frozen at 130km/h after the crash, it is alleged.

Best friends Subha Deumic and Bozica Nikolic were killed in the horror crash, which Mrs Duemic's daughter Armina - travelling behind the pair in another car - was forced to helplessly watch.