MANCHESTER, N.H. – A federal appeals court has overturned the 1997 conviction of a Bangor, Maine, man found guilty of sexually assaulting two Manchester sisters, saying he should have been allowed to question the girls about alleged false allegations of previous assaults.

The 1st U.S. Circuit Court of Appeals in Boston ruled the refusal violated Delvin White’s constitutional rights and sent the case back to New Hampshire, which must decide whether to have another trial.

The court described the Bangor man’s evidence as powerful.

“The past accusations were about sexual assaults, not lies on other subjects; and while sexual assaults may have some generic similarity, here the past accusation by the girls bore a close resemblance to the girls’ present testimony in one case markedly so. In this regard the evidence of prior allegations is unusual,” the court wrote in its decision issued Feb. 18.

“Many jurors would regard a set of similar past charges by the girls, if shown to be false, as very potent proof in White’s favor,” according to the decision.

White, 60, asked this week to be released on bail, and a judge took the request under advisement. White was originally sentenced to life in prison because of two prior sexual assault convictions in the 1970s, but the sentence was later reduced to 30 to 90 years.

The appeals court ruled White was denied the right to offer the evidence, even though the state Supreme Court, which upheld the convictions, found the prior accusations showed a “reasonable probability of falsity.”

The state court as well as trial judge James J. Barry, in Hillsborough County Superior Court, said New Hampshire law requires that in order for such testimony to be allowed, it must meet a higher standard of “demonstrably false.”

White has been behind bars for more than nine years since his March 2, 1996, arrest on charges he sexually assaulted the girls while visiting their father in his Manchester apartment.

Assistant Attorney General Nicholas Cort said his office has not decided whether it will appeal the decision. The state has until May 18 to decide.

Hillsborough County Attorney Marguerite Wageling, whose office prosecuted White, said her office is prepared to take him to trial again.