Betts v Stevens: 1910

The defendant, an Automobile Association patrolman was accused of obstructing a police constable in the execution of his duty. The police had set a speed trap, and the defendant had warned approaching vehicles of the trap. At the time they were warned they were thought to have been already speeding, and the police observed this.
Held: Bastable was distinguished on the ground that the action of the patrolman obstructed the police obtaining their timings. The gist of the offence lay in the intention with which the acts complained of were done. If the intention was simply to prevent the commission of crime, no offence was committed. It was otherwise if the intention was to prevent the commission of crime only at a time when there was a danger of detection.
Lord Alverstone said: ‘In my opinion a man who, finding that a car is breaking the law, warns the driver, so that the speed of the car is slackened, and the police are thereby prevented from ascertaining the speed and so are prevented from obtaining the only evidence upon which, according to our experience, Courts will act with confidence, is obstructing the police in the execution of their duty.’
Darling J said: ‘The appellant in effect advised the drivers of those cars which were proceeding at an unlawful speed not to go on committing an unlawful act. If that advice were given simply with a view to prevent the continuance of the unlawful act and procure observance of the law, I should say that there would not be an obstruction of the police in the execution of their duty of collecting evidence beyond the point at which the appellant intervened. The gist of the offence to my mind lies in the intention with which the thing is done. In my judgment in Bastable v Little I used these words: ‘In my opinion it is quite easy to distinguish the cases where a warning is given with the object of preventing the commission of a crime from the cases in which the crime is being committed and the warning is given in order that the commission of the crime may be suspended while there is danger of detection.’ I desire to repeat those words.’


Alverstone CJ, Darling and Bucknill JJ


[1910] 1 KB 1, 26 TLR 5


Prevention of Crimes Amendment Act 1885


England and Wales


DistinguishedBastable v Little 1907
The police had set up a series of speed traps in London Road, Croydon. Mr Little occupied himself giving warning signals to drivers approaching the traps, thus ensuring that they did not exceed the speed limit. There was no evidence that the drivers . .

Cited by:

CitedGreen v Moore 1982
The respondent, a probationer police constable was convicted for obstructing police officers in the execution of their duty under s51(3) of the 1964 Act. He was a regular in a bar he knew was to be raided. He warned the landlord who complied with . .
CitedDirector of Public Prosecutions, Regina (on the Application of) v Glendinning Admn 13-Oct-2005
The defendant had been accused of obstructing a constable in the execution of his duty by warning motorists of presence of a police speed trap. The prosecutor appealed from dismissal of the charge.
Held: ‘the hand signals given by the . .
Lists of cited by and citing cases may be incomplete.

Crime, Road Traffic

Updated: 07 May 2022; Ref: scu.235213