Jason Foster, a mechanic from Westbrook who pretended to be a police officer to intimidate prostitutes into having sex with him for free, has been convicted of eight out of 18 charges against him after a jury trial.

The jury deliberated for 4½ hours Thursday on the third day of Foster’s trial at the Cumberland County Courthouse in Portland before finding him guilty of two counts of gross sexual assault, four counts of impersonating a public servant and two counts of engaging a prostitute.

In its verdict, the jury also found Foster, 35, not guilty of 10 other charges – five counts of gross sexual assault, four counts of impersonating a public servant and one count of theft by extortion.

After the jury was excused, Justice Thomas Warren, who presided over the trial, ordered Foster taken into custody and held without bail at the Cumberland County Jail in Portland until sentencing. The judge did not immediately set a sentencing date.

Deputy District Attorney Megan Elam, who prosecuted the case, said at the start of the trial that the four women Foster intimidated were drug addicts who had turned to prostitution to pay for their drug habits and advertised on backpage.com.

Foster’s attorney, Devens Hamlen, told the jurors that his client admitted finding the four women online and hiring them for sex but denied impersonating a police officer or forcing them to have sex with him.

Foster faces up to 10 years in prison on each of the gross sexual assault charges, which are Class B felonies. He faces up to 12 months in prison on each of the misdemeanor charges of impersonation of a public servant and engaging a prostitute.