Alfred Moore, a poultry farmer and burglar, went to the gallows aged 36, seven months after the murders of the officers near his farm at Kirkheaton, Huddersfield.
He protested his innocence and accused investigating police officers of concocoting evidence against him. The gun was never found despite a huge search.
Former judge Patrick Robertshaw, who retired from the bench in 2010 after presiding over criminal trials across Yorkshire, has written a book which examines all aspects of the case against Moore and his trial.
In No Smoking Gun, Mr Robertshaw concludes that the wrong man was hanged and the evidence against him was flawed.
He says Moore was denied the most basic right of legal representation at the most crucial point in the police investigation which, he believes, “resulted in a trial that was unbalanced, unfair and with a clear potential for an unjust outcome.”
Mr Robertshaw, who lives in Scissett, near Huddersfield, wants readers to draw their own conclusions but adds: “Mine is unequivocally that the wrong man hanged, convicted on questionable evidence, buttressed by the prejudices of the age.”
The publication has been welcomed by former West Yorkshire Police detective Steve Lawson, who has spent the last five years re-investigating the case in an unofficial capacity.
Mr Lawson has written his own online account of the case - www.isthisjustice.co.uk - and he too believes that the authorities hanged the wrong man.
He passed his file to the Criminal Cases Review Commission but they declined to pass the case to the Court of Appeal, saying no new evidence had come to light.
“The new book backs up everything I have been saying for years, that Alfred Moore was innocent of the crime.”
The new research had given “peace of mind” to the three surviving daughters of Moore, he said.
* No Smoking Gun is published by Authors OnLine Ltd, priced £9.99. Details by email: [email protected]