PORTLAND, Ore. (AP) — An Oregon judge has thrown out statements made by a man accused of killing four women, finding that Portland police used improper and coercive tactics during the interrogation.

Homer Lee Jackson, 57, was arrested in October 2015 in the strangling deaths that occurred in the 1980s. After Jackson was apprehended, police questioned him for more than seven hours over two days, The Oregonian/OregonLive reported .

Earlier this month, Judge Michael A. Greenlick suppressed the statements obtained by two detectives during the interview. Authorities said the statements were a confession by Jackson.

The detectives, using an array of tactics, encouraged Jackson to confess to killing the women. At one point during the interview, a detective urged Jackson to "get on" the train, and then warned that if Jackson didn't, he would be "run over" by the train, according to transcripts of the interrogation.

The judge cited more than a dozen examples from the interrogation that demonstrated the statements were "made under the influence of fear produced by threats." The judge said that the types of inducements or threats made by police can create a risk of an inaccurate admission.

"Given the totality of circumstances, I believe the defendant could have started to believe that he would suffer a number of detrimental consequences, including that the judge and the jury would consider him to be a monster, the police would seek the longest possible penalties, the victims would be angry and influence prosecution negatively," the judge said.

Prosecutors have defended the detectives' methods and said the statements were given voluntarily.

"There is simply nothing threatening about calling the defendant a monster nor is it threatening to tell the defendant that the detectives will work as hard as possible to do their jobs and make a strong case against the defendant in order to keep him in prison as long as possible," Deputy District Attorney Susan O'Connor said. "A threat must be more than expression by the officer of an intent to do something that the officer is authorized to do."

Jackson has pleaded not guilty to charges of aggravated murder.

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Information from: The Oregonian/OregonLive, http://www.oregonlive.com