Updated Monday, March 23rd 2009, 12:48 PM
The grand jury charged Monserrate (D-Queens) with three counts of felony assault on girlfriend Karla Giraldo and three counts of misdemeanor assault.
The former City Councilman, sworn into the state Senate in January, is expected to be arraigned later this week.
He faces up to seven years in prison, if convicted.
Giraldo needed more than 20 stitches near her left eye because of the attack inside Monserrate's apartment Dec. 19, 2008, prosecutors said.
The petite 29-year-old first told staffers at Long Island Jewish Medical Center she got the cuts from a fight with Monserrate, prosecutors said.
Giraldo later changed her story, submitting a sworn affidavit saying it was all an accident.
She said Monserrate tripped on her shoes while bringing her a glass of water in bed, court documents show. She accused police of trying to get her to incriminate Monserrate.
Prosecutors said the fight began after Monserrate found another man's business card in Giraldo's purse.
Surveillance video from inside Monserrate's apartment building showed him yanking Giraldo by the arm as she clutched a stairway banister. It also caught her banging on a neighbor's door while screaming for help, prosecutors said.
Sources said Giraldo testified before the grand jury that the injuries were accidental. They said Monserrate did not testify.
Monserrate released a statement through a public relations firm in which he denied wrongdoing.
"I've said all along this was an accident," he said. "Karla has said all along this was an accident. The district attorney's politically motivated decision to pursue this case doesn't change the fact that this was an accident."
A source close to Monserrate said his lawyers will ask for a special prosecutor to handle the case. The source said the lawyers declined a plea deal offer from prosecutors last week.
Monserrate and District Attorney Richard Brown have feuded publicly over a series of contentious murder cases.
Monserrate criticized Brown's handling of Queens College student Manuel Mayi's 1991 murder, accusing the office of misplacing key court documents and transcripts when the NYPD cold case squad reopened an investigation in 2005.
Brown accused said Monserrate was misstating the facts.
Monserrate also blasted the top Queens law enforcement officer for failing to prosecute a retired NYPD detective who accidentally shot an 18-year-old Mexican bodega worker in the chest in 2004.