William Henry Kennedy was born in 1891 in Ayrshire, Scotland, to Irish parents. His early life was marked by instability and criminal behavior. Trained as a compositor, he worked primarily in Liverpool but frequently found himself on the wrong side of the law. His criminal record included convictions for robbery, assault, drunkenness, and indecent exposure.​

Kennedy's military service was equally tumultuous. He enlisted in the Loyal North Lancashire Regiment in 1903 under the alias William Herbert and served until 1911. During World War I, he had multiple stints in the army, often deserting and re-enlisting under different names, including Patrick Mane Fitzpatrick and Michael Sullivan. His military career was marred by desertions and criminal activities, leading to several imprisonments.​

After the war, Kennedy continued his criminal pursuits. In 1927, he was employed by Frederick Guy Browne, a fellow ex-convict, at a garage in Clapham, London. The garage served as a front for their illegal activities, including car thefts and burglaries.​

On the night of September 26, 1927, PC George Gutteridge was on patrol near Stapleford Abbotts, Essex. Around 3:30 AM on September 27, he stopped a suspicious blue Morris Cowley car driven by Browne, with Kennedy as the passenger. While Gutteridge was taking notes, Browne shot him twice in the cheek and once in each eye, killing him instantly. The motive was to prevent identification.​

The stolen car was later found abandoned in Brixton, London. A cartridge case marked RLIV, indicating World War I-era ammunition, was recovered from the vehicle. Ballistics expert Robert Churchill matched the cartridge to a Webley revolver found in Browne's possession during his arrest on January 20, 1928.​

Kennedy fled to Liverpool, where he sought refuge with acquaintances. On January 25, 1928, Liverpool police attempted to arrest him. During the arrest, Kennedy pulled a loaded firearm on Sergeant Mattinson, but the gun misfired, and he was apprehended.​

In custody, Kennedy admitted to being present at the murder scene but claimed Browne was the shooter. Despite his confession, both men were tried together at the Old Bailey. The trial began on April 23, 1928, and concluded on April 28. Both were found guilty and sentenced to death.​

Kennedy was executed by hanging at Wandsworth Prison on May 31, 1928. Browne was executed simultaneously at Pentonville Prison.