A new indictment alleges that a former Cravath, Swaine & Moore tax attorney had sex with a third child in addition to the two sisters he has been accused of raping.

The Manhattan district attorney’s office announced the indictment yesterday in state Supreme Court in Manhattan with the defendant present. When he was arraigned on the new charges, James Colliton, 42, said in a loud voice: “Absolutely not guilty.”

The new indictment alleges that between Christmas Day 2000 and January 2002, Mr. Colliton committed 38 counts of third degree rape and four counts of sodomy. Mr. Colliton’s attorneys, Howard Greenberg and Kathleen Mullin, said they did not know for certain the identity of the alleged victim.

Assistant District Attorney Rachel Hochhauser said in court that the victim was 15 when Mr. Colliton’s relations with her began.

Ms. Hochhauser said the victim included in the new indictment was not related to Mr. Colliton’s other two accusers, who are sisters. The two sisters, who are now 21 and 15, allegedly each had sex with Mr. Colliton and one is said to have lived for a time in his Manhattan apartment as a young teenager. The mother of the two girls had been accused of being complicit in her daughters’ alleged involvement with Mr. Colliton. She pleaded guilty to a charge of endangering the welfare of a child last week.

Ms. Mullin said the length of time between the alleged crime and the current indictment “casts credibility issues” on the latest accusations.

Mr. Colliton was arrested in the East Village on March 3. Days earlier, Canadian law enforcement officers had apprehended him and then inexplicably released him. Since his arrest, Mr. Colliton has been detained at Rikers Island and has not yet filed for bail. Mr. Colliton is from Poughkeepsie, where he has a wife and five children.