First-degree manslaughter carries a maximum penalty of 25 years in prison. Rodriguez also was convicted of endangering the welfare of a child.
"I am grateful that at least they're holding him accountable with a manslaughter conviction," Assistant District Attorney Alma Dwimoh said.
Evidence in the nearly three-month-long trial in state Supreme Court included grim crime scene photos from the room where Nixzmary Brown was bound to a chair, starved and forced to urinate in a litter box. More than once, court officers passed out tissues so weeping jurors could dry their eyes.
In closing arguments, prosecutor Ama Dwimoh displayed a large photo of the victim's body -- bruised, topless and splayed on a wooden floor in the family's ramshackle apartment -- as she stood in front of the defense table and berated Rodriguez.
"You battered a little girl who weighed 36 pounds," she said last week. "When she was on the floor in that room you imprisoned her in, you turned your back."
Gazing up at the photo, she argued: "There is nothing that 7-year-old Nixzmary Brown could ever do to deserve that."
Despite the emotion surrounding the case, defense attorney Jeffrey Schwartz stuck to a bold strategy of casting Nixzmary's mother as the real killer, labeling her "Mommy Dearest."
He also portrayed the victim as a violent and uncontrollable "little Houdini" -- a reference to her supposed knack at slipping out of the makeshift restraints devised by her parents to keep her from attacking her younger siblings.
Schwartz asked the jury of two men and 10 women to focus on the testimony of a jailhouse snitch, who claimed that behind bars the mother, Nixzaliz Santiago, described a fatal beating.
It was "the confession of the sick, of the demented, of the disturbed mother," he said.
Rodriguez, 29, pleaded not guilty to murder, manslaughter and other charges in connection with the girl's death on Jan. 11, 2006.
In a videotaped statement played for the jury, Rodriguez said that on Nixzmary's last night, he punished her by sticking her head under running bath water "to make her think." Investigators suspect the girl's head was smashed against the faucet -- something her stepfather denied doing.
The stepfather admitted he had abused her but denied killing her, saying on tape, "Sometimes she'd get me real angry, and I used to just throw her on the floor. ... She was always lying to me about everything."
Schwartz contended that Rodriguez was a hard-working security guard and overwhelmed parent who was "guilty of child abuse." But he said the case was plagued by sloppy police work and a rush to judgment, and told jurors, "You have not seen evidence in this courtroom that has proven murder or manslaughter charges."
Schwartz also sought to blame the city's overburdened Administration for Children's Services for doing too little to stop it.
There had been warning signs for years before the little girl died. School employees had reported that she had been absent for weeks the previous year.
Neighbors noticed unexplained injuries and noted she appeared underfed and small for her age. Child welfare workers had been alerted twice but said they found no conclusive evidence of abuse.
The case, coupled with a series of other high-profile deaths of children known to child welfare workers, sparked public demands for reform.
City officials and lawmakers responded by bolstering the corps of caseworkers and drafting legislation to give life in prison without parole to parents who cause the death of a child under 14 through abuse.