Police are currently investigating 56 unsolved murders – including that of a Birkby man who disappeared from home more than five years ago.
The Examiner revealed how Dariusz Michalowski’s disappearance in March, 2011 was being treated as murder even though a body has never been found.
Now a Freedom of Information request to West Yorkshire Police has found that the force is investigating 56 murders dating back to 1975.
Last year extra cash was allocated to employ more police staff to crack ‘cold cases.’
A force spokesman said: “West Yorkshire Police are currently undertaking a review to understand the outcomes of investigations into previous homicides.
“This includes review of all cases where suspects were charged but were subsequently acquitted in court. This may have been for numerous reasons and understanding this is crucial.
“These cases are currently classified as ‘Detected’ under previous crime outcome recording methods therefore any data provided is subject to change.”
Det Supt Jim Dunkerley added: “In common with other police forces, West Yorkshire Police has homicide cases which remain unsolved, most of which are historic in nature.
“West Yorkshire Police are continuing with an ongoing process to review non-recent undetected offences in line with national guidance around the handling of information, and in conjunction with the Home Office under the requirements of the Public Records Act.
“Should any new lines of enquiry be identified, they will be comprehensively pursued.”
Cases under review, in chronological order, include:
* Renee McGowan, 55, who was found strangled in her 14th floor flat in Evans Towers, off Manchester Road, Bradford, on July 23, 1975.
* Deborah Schlesinger, 18, who was murdered in 1977 in Leeds. Yorkshire Ripper Peter Sutcliffe has been suggested as a suspect in some news reports.
* Harold Day, 73, was found strangled in his flat at Beaumont Court, Batley, in 1979.
* William Smith, 56, who was murdered while walking on an unlit path near to Mirfield Memorial Park in October 1986. In October detectives said they believed someone local will know the killer. A post mortem found he had been asphyxiated.
* Laurence Winstanley, 23, whose body was found trussed up and dumped in Baitings Reservoir, near Ripponden, in 1988. The Oldham man had been shot in the head.
* Doris Kellett, 92, who was clubbed to death at her home opposite Cleckheaton police station in January 1990.
* Yvonne Fitt, 33, of Bradford, whose body was found in a shallow grave near Otley in September 1992.
* Sarah Lewin, a mother-of-three who was battered to death at her home in Bradley Boulevard, Sheepridge, on January 14, 1994.
* Brian Hardwick was shot dead by someone who had punctured his car tyre to make him stay after his colleagues left Huddersfield Car Electrical Services on Colne Road on November 21, 2001.
* Jasem Asakerh, who was shot as he sat in the back of an Audi Q7 in Thornton Lodge in April 2009.
* Dariusz Michalowski, 44, who disappeared from his Birkby home in March 2011. Three men were arrested last year but were released without charge.