Elaine Whitfield Sharp said witnesses claimed to have seen baby Matthew Eappen fall on to his head from a trolley in a south Boston toy shop while out shopping with his father Sunil.
The alleged accident happened around Christmas 1996 - just weeks before Louise was arrested on suspicion of murdering the eight-and-a-half month- old baby boy. Much of the evidence in her trial centred on defence claims that the child had died from an old injury that had started to bleed again, probably as the result of a minor bump.
Ms Whitfield Sharp said she believed one of the witnesses in the toy shop gave a video-taped interview to the New England Cable News Company during the trial. She added that the two sets of people who claimed to have seen the child fall on his head came from "completely different walks of life" but they "corroborated one another".
The American lawyer also claimed that members of the Silver, Glate and Good defence team received the information during the trial but failed to investigate the allegations.
Ms Whitfield Sharp said she first learned of the evidence during Louise's appeal and has since interviewed two of the witnesses and spent around $20,000 (pounds 12,500) of her own money investigating the claims.
She hopes the fresh evidence will be brought into the public domain as part of a defamation case brought against her by a state trooper.
The lawyer, who claims she resigned from Louise Woodward's prosecution team, was questioned by state trooper Randy Cipoletta after a routine stop of her car.
He claimed that she told him in a roadside confession that she believed that Louise,from Elton, Cheshire, was guilty. When Ms Whitfield Sharp accused him of making a false report, he sued for defamation.
The lawyer now claims that at the time of the routine stop she was paying a private investigator out of her own funds to pursue witnesses who claimed to have seen Matthew fall from the toy store trolley.
"I want this out in the open. I have taken it as far as I can and would like other witnesses to come forward. If we had this during the trial, we could have stopped that train, gone to the judge and said look at this.
"We could have avoided the conviction of someone who is innocent. I want this to be made public and just hope something good comes out of it for Louise."
Peter Quinn, Louise Woodward's Liverpool-based solicitor, said last night: "Our initial reaction is one of caution.
"Before we comment further we need to know what specifically this witness is saying. We shall be contacting the lawyers in the United States who have the conduct of the defence in the morning for further information. But we will not be commenting further until then," said Mr Quinn.
Louise Woodward was convicted of second-degree murder, reduced to manslaughter by trial judge Hiller Zobel, who sentenced her to 279 days of "time served" - equal to the period she had spent in custody awaiting trial. She is now studying law at South Bank University in London.Reuse content