Mr Brafman also said he would investigate what he said had been "perjury" before the grand jury which indicted Mr Weinstein, as well as the conduct of a NY police officer who had worked on the case.
"The integrity of these proceedings has been compromised", Mr Brafman said.
The New YorkPost, never known for its restraint, blasted out a headline just before the judge dismissed the sexual assault count, wondering if the D.A.'s case is "in danger of falling apart".
Ms Evans has told USA media that Mr Weinstein forced her to perform oral sex on him in 2004.
"I want to be very clear that prosecutors' decision to abandon my client's claims does not invalidate the truth of her claims", Ms Goldberg said.
The witness told prosecutors that she and Evans met Weinstein in a bar during summer 2004.
He walked into the criminal court in downtown Manhattan dressed in a dark suit, tie and white shirt for the brief hearing that scored at least an initial win for his defence attorney Ben Brafman.
Film producer Harvey Weinstein sits during his hearing at Manhattan Criminal Court in N.Y., October 11, 2018.
Weinstein's lawyers and prosecutors had been wrangling over the part of the indictment pertaining to Evans' allegations over the last few weeks in closed-door meetings and sealed court papers.
A source familiar with the investigation told CNN at the time that the criminal sex act charge was from a case involving aspiring actress Lucia Evans, who alleged Weinstein forced her to perform oral sex on him in his Tribeca office in 2004.
The witness alleges that Evans later agreed to give Weinstein oral sex in exchange for a movie role.
Carrie Goldberg, an attorney for Evans, spoke to reporters outside the court in lower Manhattan following the dismissal.
The letter also said prosecutors had recently obtained an email that Evans wrote in 2015 to the man she later married. "It only speaks volumes about the Manhattan DA's office and its mishandling of my client's case".
The numerous sexual misconduct accusations made against Weinstein, namely those made out of court, had raised awareness of the #MeToo movement and increased public debate about the issue of consent.
Harvey Weinstein's attorney says an accuser should be criminally prosecuted for perjury following the decision to drop part of the case against him.
It reportedly comes after the district attorney's office discovered a previous written account by Evans which could suggest that her sexual encounter with Weinstein was consensual. At the time, Vance cited a lack of supporting evidence, despite the existence of a clandestinely made recording of Weinstein discussing the episode with the woman.
Weinstein has pleaded not guilty and is free on $1 million bail.
New York Police officials poured on the pressure, too, saying publicly that they believed they had gathered ample evidence to make an arrest.
Grieving bride spends her wedding day at grave side
The final stop was Murphy's grave. "I've been dreading this day for a really long time". "I wanted to be where he was at". In another photo shared by Padgett on Facebook , a photo of her wearing her wedding dress can be seen.