The Court Case

This is a true story. This happened many years ago, and was told me by a man with spare time on his hands, who used to spectate in court to pass some of that spare time. Lawyer - "You say you saw the defendant's car involved in a road accident at the junction of X and Y?" Policeman - "That is correct." L - "And where were you at this time?" P - "At the junction of X and Z." L - "So you were some 80 yards away when the incident occurred?" P - "Yes, I was." L, in incredulous accent - "So you were 80 yards away, but you say you knew this vehicle had been involved in an accident?" P - "Yes." L - "Then please tell the court how you knew this vehicle went through a red light?" P - "Because the light that I could see was green." L, triumphantly - "Ah, but how did you know that it had been in an accident?" P - "Because it went past on its roof."