He has labelled one fifth of the force awful and claims a large number of statements were concocted before being signed by a suspect.
Former Judge Anthony Murphy, who sat for many years on the Cork circuit launched his attack at the end of a miserable week for the embattled force. Some of its members, still reeling from the Morris Tribunal allegations were criticised by the Garda Complaints Board for wholesale non-cooperation with the May Day march investigation.
Senior gardaí last night said Judge Murphy who colleagues say was rarely, if ever, publicly critical of the force during his career on the bench, was entitled to his opinion.
One garda said: "In a recent survey there was an 87% satisfaction rating."
Judge Murphy, asked whether he presided over cases where he felt a confession had been tampered with or was false, said: "I think the position in a large number of cases is that a guard will write, clearly and sequentially, what he thinks should be the order of battle and he gets the man to sign it. That is not how to take a statement.
A statement is taking down the words of the man. Analysing a lot of statements I've read they couldn't have been the words of the men."
He made the comments during a discussion on RTÉ's Prime Time programme.
Commissioner Pat Byrne this week defended the force, particularly in relation to claims that they were unable to carry out investigations into its own members.
"While it can be described as scandalous when people see gardaí being convicted in the courts, it must never be forgotten who interrogated them, gathered the information and brought them before the courts." It has emerged that 79 members of the force have been charged with various offences since January 2000. These charges include larceny, bribery, drink driving and child porn.
An independent inspectorate is to be set up to replace the Garda Complaints Board. Its investigators will have to be experienced in criminal investigations and will include former gardaí, ex-police from outside the jurisdiction and criminal lawyers.