(CNN) -- For about six months, Daniel Holtzclaw preyed on women in one of Oklahoma's poorest neighborhoods, exploiting his police badge to intimidate them into keeping quiet.
Prosecutors say the Oklahoma City officer picked out his victims based on their criminal histories, figuring their drug or prostitution records would undermine any claims they might make against him.
Then, he would subject them to assaults that escalated from groping to oral sodomy and rape.
On Thursday, his 29th birthday, Holtzclaw rocked back and forth in his chair and sobbed as the judge read out the verdict.
After more than 40 hours of deliberation, the jury had found him guilty of 18 of the 36 charges he faced, including four counts of rape in the first degree and four of forced oral sodomy.
More than 250 years of prison recommended
The jurors recommended a total of 263 years of prison time for Holtzclaw's crimes. Formal sentencing is set for next month.
"We're going to ask the judge to make sure that this defendant never sees the light of day," District Attorney David Prater said. "And we're going to ask him to run consecutive, every count."
Holtzclaw was a former star linebacker on the Eastern Michigan University football team with a degree in criminal justice.
His ruthless scheme started to unravel after one woman told authorities he had assaulted her during a traffic stop in June 2014.
In the months that followed, investigators pieced together the horrifying scale of his pattern of abuse.
He was fired from the force in January after an internal investigation.
"Your offenses committed against women in our community constitute the greatest abuse of police authority I have witnessed in my 37 years as a member of this agency,' Oklahoma City Police Chief William Citty wrote in the termination letter, according to CNN affiliate KFOR.
Holtzclaw's trial began in early November and was criticized by activists after an all-white jury was chosen to decide on crimes committed against black women. Protesters repeatedly gathered outside.
Holtzclaw, whose father is white and mother is Japanese, is identified as "Asian or Pacific Islander" by court records.
17-year-old raped on mother's porch
Thirteen women accusing him of sexual assault testified in the trial.
"I didn't think anyone would believe me. I'm a black female," one accuser said in court, according to The Oklahoman newspaper. Another said Holtzclaw told her would get rid of a drug charge against her if she cooperated with him.
The assaults took place in range of places, including in his police car. One young woman, only 17 at the time, was raped on her mother's front porch.
"He didn't choose CEOs or soccer moms; he chose women he could count on not telling what he was doing," the prosecution said in its closing statement this week.
The defense questioned the credibility of Holtzclaw's accusers, arguing some of them were high when the purported assaults took place. It also challenged the validity of DNA evidence.
Prater, the district attorney, said that the jurors' decision not to convict the former police officer on half of the counts against him didn't necessarily mean they didn't believe some of the women.
"It may mean that we didn't meet our burden in those counts," he said.
Police department: 'Justice was served'
Holtzclaw, whose father is a police lieutenant on another force, waived his right to testify.
The Oklahoma City Police Department welcomed the verdict against its former employee.
"We are satisfied with the jury's decision and firmly believe justice was served," it said.
Some women gathered outside the Oklahoma County Courthouse celebrated Holtzclaw's conviction by mockingly singing "Happy Birthday," KFOR reported.
But others, including one of the victims' mothers, said they were waiting for the formal sentencing before deciding whether justice had been done.
CNN's Michael Martinez and Gigi Mann contributed to this report.
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