Brian McKay, 46, of Lightcliffe Road, Huddersfield, was found not guilty of shoulder barging Stefanie Pogson, who was 38 weeks pregnant, while she was out shopping with her partner on January 22.
Mr McKay denied he was there and told his trial at Kirklees Magistrates Court he was working at Armley Prison in Leeds at the time.
Police failed to interview Mr McKay to verify his whereabouts and District Judge Michael Fanning slammed the investigation and said: “This is a half-cocked police enquiry.”
The court heard how Mr McKay was a client of employment advisor Ms Pogson who helped him find work after living on benefits for more than a year.
She told the court in evidence: “We were walking towards the exit and coming up to the jewellers. I saw Mr McKay coming quite widely round the corner with a fixated gaze on me.
“He was walking towards me with some intent. I was walking relatively slow pace as he came towards me veering towards my right shoulder.
“It was a recognisable movement.”
She told the court her partner asked her: “Did that guy just barge into you?”
The court heard Ms Pogson stopped briefly in TK Maxx and was ‘shaken’ by what had happened.
She then continued walking and phoned police as she got to her car on Station Street.
The court heard Mr McKay was summoned to appear at court and was not interviewed by police.
District Judge Michael Fanning said: “This is a half-cocked police enquiry.”
He then questioned the defendant as to why – if he was in fact at work – did he not bring the paperwork to prove it.
Mr McKay said he wasn’t asked to bring it.
The judge added: “I have no doubt that Ms Pogson believes he is the person who shoulder barged her.”
But he said “ghastly errors” had occurred in other cases with identification and no witness evidence could be provided to the contrary.
He said police failed to ask the victim’s partner to attend an identity parade which could have assisted the case.
He said it was up to the Crown to prove a negative alibi.
The judge decided the case on the evidence before him that Mr McKay was not guilty of assault and he was free to leave court.