Between December 2003 and February 2004, at least 17 patients suffered respiratory arrests for then-unknown reasons. While 15 patients recovered soon after, two patients died in January 2004: Anthony Bateman and David Onley.
Geen, who was on duty during these incidents, was arrested on February 9, 2004, whereupon a syringe filled with a lethal dose of muscle relaxant was discovered in his pocket.
The hospital found 27 cases that Geen could have been involved in, though 9 were discounted and Geen was acquitted of one other case.
During his trial, the Oxford Crown Court was told that Geen purposely used potentially lethal doses of drugs to cause patients to stop breathing because he enjoyed the thrill of resuscitating them. He was found guilty in April 2006, and the trial judge recommended that he should spend at least 30 years in prison before being considered for parole. This recommendation is likely to keep him behind bars until at least 2035.