Bill Cosby's bid to defeat a sexual assault suit by actor Lili Bernard just got more complicated after an organization headed by University of Pennsylvania professor Marci Hamilton took aim at his defense theory.

Senior U.S. District Judge Noel Hillman allowed Hamilton's group, Child USA, to join the case as amicus on Thursday. On the same day, Child USA submitted a 53-page brief opposing Cosby's motion to dismiss the suit.

Doing battle with Hamilton, an authority on preventing child sexual abuse, will add to the challenges facing Cosby in the case.

Child USA's brief says Hamilton is the "foremost constitutional scholar" on laws changing statutes of limitations on sexual assault, and "has advised Congress and state governors, legislatures and courts on the constitutionality of revival window laws for child sex abuse throughout the United States."

Bernard, who guest starred on the "Cosby Show" in 1984, claimed in her 2021 suit that Cosby lured her to an Atlantic City hotel, where he drugged and sexually assaulted her. Bernard's suit said the alleged assault took place in 1990, when she was 26. Bernard brought the suit under a New Jersey law that relaxed the statute of limitations for certain sexual assault claims.

Cosby has moved to dismiss the case, claiming that the statute, N.J.S.A. 2A:14-2b, is unconstitutional when applied to alleged assaults of adults such as Bernard. The law in question, enacted in 2019, has played a rule in numerous suits accusing clergy and Boy Scout leaders of sexual abuse of minors.

Cosby argued, among other things, that the statute violates due process where it is unconstitutionally vague and where it retroactively deprives him of his statute-of-limitations defense, which is a vested right.

Cosby's lawyer in the case, Jennifer Bonjean of Bonjean Law Group in New York, said she had "no objection to Child USA filing an amicus because it underscores our position that the statute is designed to address child sexual abuse—not untimely claims from adults."

Bonjean said elements of Child USA's argument supported her position that the statute should only apply to allegations of abuse against children.

"There's a certain uniqueness about children in terms of their ability to come forward that doesn't apply to adults. Our argument highlights the differences between child victims and adult victims. Child USA discusses the legislative history behind the statute and why it's so important that the lookback window applies because of the unique crime of child sexual assault. They discuss the origins and why it was created in the first place. It was never intended to encompass adults, if you look at the legislative history," Bonjean said.

Hamilton, in an email, said of her involvement in the case, "The court's decision marks a historic day for survivors, who deserve to have the court's focus on social science and deep dive legal analysis, rather than the last-ditch defenses of the rich and powerful defendants. Cosby has been able to avoid justice for decades due to bad statutes of limitations and scorched earth tactics against victims. These cases turn marginalized and silenced victims into vindicated and thriving survivors."

Child USA's brief says the statute's legislative history demonstrates a clear intent for the revival window to apply to both children and adults, based on similar policy concerns.

The standard statute of limitations for civil suits over sexual abuse is two years. The bill extended that to age 55, or seven years after discovering the injury for those who were abused as minors. For adult victims, the suit must be filed within seven years of discovering the injury.

But Child USA cited a statement by a sponsor of the statute, Sen. Joseph Vitale, D-Middlesex, in a legislative hearing. "For a child or adult, [sexual abuse] is the single most violent life changing event that will ever happen to them. They carry that with them for the entirety of their lives. This bill equally applies to all victims, both children and adults, so they are given a fair and reasonable amount of time to bring their case regardless of when the abuse occurred," Vitale said.

Child USA also said Cosby's claim that most states recognize an absolute constitutional vested right in a statutes-of-limitations defense is "patently false."

A minority of states adheres to a vested rights approach to statutes of limitations but that is "not compelling because it directly conflicts with New Jersey law which does not grant defendants an absolute right to such a defense. The revival of an expired civil statute of limitations has been regularly upheld in other contexts in New Jersey," Child USA argues in court papers.

Hamilton's co-counsel is Hillary Nappi of Hach Rose Schirrpa & Cheverie in New York. Jordan Merson of Merson Law in New York, is representing Bernard. Merson failed to return a call for comment.