A judge ruled there was insufficient evidence to prove Cameron St Rose was at the 74-year-old’s Abington home when he was attacked in 2015.
The case is again one of more than 20 unsolved killings in Northamptonshire Police files — some dating back nearly 70 years.
On October 25, 1952, in the sleepy village of Ashton, near Oundle where popular gamekeeper George Peach, 64, and 67-year-old wife Lillian Peach were beaten to death at home in the middle of the night.
More than 100 men were questioned, but police could not make anything stick.
A teenager was also acquitted in 1988 of murdering 13-year-old Carol Baldwin who was stabbed in the chest in a park in Northampton. Elemer Patakfalvi was arrested and charged but prosecutors dropped the case against him.
Other horrific cases include the body of a baby who has never been unidentified after being discovered strangled and wrapped in cloth near Northampton train station in May 1982.
■ Cyril Fensome, 62, Florence Pennell, 60, and seven-year-old Stacey Darlington all died when petrol was poured through a letterbox in Northampton and set alight in 1987.
■ Three-year-old Callum Bland also died following an arson attack outside his home in Wellingborough in March 2007.
■ The body of Avis West, 82, was found by a neighbour after she was murdered at her home in Northampton in 1976.
■ Susan Ovens and Sidney Hickling, both 27, and Dolphus Smith, 57, were all shot at close range in their Rushden caravans in 1981.
■ Pensioner Percy Francis, 70, was stabbed and hit with an object in Rushden in 1988.
■ Twenty years ago, Mithat Lleshi, 23, and Astrit Cakoni, 28, were attacked outside a Northampton shop.
■ Abdi Leban, 32, died in a suspicious fire in a block of flats in Northampton in 2008.
■ Police launched a murder enquiry in 2015 into the disappearance of Helen Gormeley, 64, in 1986.
■ Albert Bowers, 57, died of a blood clot in 1998 after being beaten in Northampton.
Anyone with information on any of these cases can contact Northamptonshire Police on 101, or call Crimestoppers anonymously on 0800 555111.
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