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Undercover police officer stress claim, misuse of drugs and ex turpi causa

A claim by an undercover police officer who suffered psychiatric injury after being confronted with his own misuse of cocaine during a deployment…

AB v Chief Constable of X [2015] EWHC 13

Executive summary

A claim by an undercover police officer who suffered psychiatric injury after being confronted with his own misuse of cocaine during a deployment failed. The officer had not shown that his psychiatric injury had been caused by any breach of duty of care by the chief constable and even if breach had been established, the legal principle of ex turpi causa would have prevented any damages being awarded.

The facts

The claimant, an undercover police officer, claimed damages for psychiatric injury arising from alleged breach of duty of care owed to him by his chief constable.  He admitted that, while on undercover deployment, he had misused cocaine on a number of occasions and had not reported this to anyone.  His misconduct was eventually discovered and he was removed from operations. He suffered with a chronic adjustment disorder and subsequently took ill health retirement. 

He claimed damages for personal injury and financial losses flowing from his premature retirement.  It was alleged his chief constable had breached his duty of care by failing to provide appropriate support during the claimant’s period undercover.  The police denied liability and any breach of duty, alleging that any psychiatric injury was attributable to the claimant’s own misconduct in abusing cocaine and his sudden fall from grace when that was discovered. 

The decision

Mr Justice Males found there was no objective evidence of any symptoms of psychiatric disorder before he was confronted with his misconduct by his supervising officers.  The court rejected the claimant’s evidence that the disorder had arisen as a result of his excessive exposure to undercover work, compounded by a lack of support and supervision.  Instead, Mr Justice Males found it had been caused by his sudden loss of status and identity as an undercover officer when confronted with the misconduct.  The claimant immediately realised that he would never work again as an undercover officer, and that was causative of his injury. 

The chief constable had an appropriate system for psychological monitoring, and the claimant was regularly seen by other officers who noticed no change in him.  The measures identified were reasonable and had been implemented properly.

Even had the claimant proved breach of duty, the claim would have failed.   The illegality principle of ex turpi causa applied (see Gray v Thames Trains Limited [2009] UKHL33 [2009] 1AC1339) and to allow the claimant to claim successfully for psychiatric injury caused by his own criminal misconduct would compromise the integrity of the legal system. 


This is a sensible and welcome decision in an area of policing currently in the media spotlight. The judge’s application to the facts as he found them of the well-known Hatton guidelines and the ex turpi causa doctrine denied the claimant any remedy.  The chief constable had in place appropriate measures and a rigorous system of supervision and monitoring: it was the claimant’s own decision to take cocaine which led to his downfall. A salutary tale!

For further information about Weightmans or to discuss any of the issues in this update, please contact Andrew Clarke, Partner, on 0116 261 6422 or email

Andrew also acted for the chief constable in this case.