My hon. Friend is certainly right that it is absolutely vital that the devices used in police stations to provide conclusive evidence that a person has drugs in their system are 100% accurate. We are on the threshold of having type approval for such devices. I am dealing with screening devices that could be used at the roadside and that are comparable to the devices used to identify those suspected of drink-driving. Those screening devices, which people have to blow into through a tube, indicate prima facie whether there is excess alcohol in the system. It might turn out that those people, even if they have a positive breath test, are found not to test positive when they get down to the police station and a blood sample is taken. The device is a screening device. It enables the police, following road traffic accidents or offences, to screen people they suspect of having alcohol in their system. I am suggesting that we urgently need a similar system for people who are suspected of having drugs in their system.