The basis for the motion filed by Ben Brafman said prosecutors withheld evidence when presenting the case to the grand jury, such as friendly emails that one of Weinstein accusers sent to him.
Further, the friend and her attorney told the DA that DiGaudio said, "going forward, 'less is more;' and that the Witness had no obligation to cooperate".
Weinstein was once a juggernaut in the entertainment industry until a pair of Pulitzer Prize-winning stories from the New York Times and the New Yorker published in October 2017, detailing accusations from several women.
In another blow to the case, prosecutors obtained a 2015 draft email that Evans wrote to her husband, who was then her fiancé, in which she recounted the encounter with Weinstein.
Assistant District Attorney Joan Illuzzi-Orbon, the lead prosecutor in the case, insisted that the agreement to drop the count would have no bearing on the case's resolution. Rather, "it only speaks volumes about the Manhattan D.A.'s office and its mishandling of my client's case".
"The evidence shows that the criminal case against him is strong", the statement said.
Following the hearing, the office of Manhattan District Attorney Cyrus Vance made public a letter it had sent to Brafman last month disclosing that an unnamed witness had told them that she had heard an account of the alleged assault from Evans that was different from the one Evans originally gave to Vance's office. Evans claims Weinstein forced himself on her, but the witness says otherwise. "Nor does it reflect on Lucia's consistent allegation that she was sexually assaulted with force by Harvey Weinstein", lawyer Carrie Goldberg said.
Robertson: Title race not just a two horse race
Liverpool are now level on 20 points with Manchester City and Chelsea at the top of the Premier League after eight games. When I see one player take the ball and dribble past three, four or five players and score the goal, it depends on him.
Disgraced movie mogul Harvey Weinstein has one less count of sexual assault being brought against him before his trial begins.
A lawyer for Evans said they were disappointed by the decision, saying in a statement the district attorney abandoned their client.
The development was announced in court on Thursday with Weinstein looking on.
Weinstein has been accused by more than 70 women of sexual misconduct in the past year.
The defense said it would also subpoena police interview records after claiming an NYPD detective "may have unfairly tainted these proceedings" when he prepared Evans for her testimony.
Weinstein has denied all the charges.
Weinstein's defence lawyer later suggested, outside court, that Ms Evans should be criminally prosecuted for perjury. Weinstein had promised to get her an acting job if she agreed to perform oral sex, and she agreed, it said. 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.
There are still five criminal charges against the embattled producer involving two other women. The Associated Press does not identify alleged victims of sexual assaults unless they come forward publicly, as Evans has done. Weinstein has pleaded not guilty to all the charges.