Its the sole responsibility of the person driving the car to pay for any cost occured during the hire period. Whether its a traffic violation or accident. To safeguard their side the rent a car companies always has guarantee cheque before they rent out the car. Your friend will have to pay 6000 QRs or else he will have to take the matter to court where again he will be asked to pay the amount. This is what put me off when i think of settling in Qatar. If the police say something the authorities believe it blindly. I recollect one of my colleagues paid a fine of 3000 riyals for this same nonsense and injustice.