Updated 10/29/14 – 11:26 a.m.

CHICAGO (CBS) — A week after he was held in contempt of court for refusing to speak to a judge, suspected serial killer Darren Vann politely answered the same judge’s questions, and pleaded not guilty to the murders of two women whose bodies were found in northwest Indiana earlier this month.

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Vann, 43, has been charged with two counts of murder, for allegedly strangling 35-year-old Anith Jones and 19-year-old Afrikka Hardy, although police have said he confessed to killing at least five other women whose bodies were found in Gary and Hammond nearly two weeks ago.

He made his first court appearance last Wednesday, but said absolutely nothing when a judge asked him three times if he intended to tell the truth and cooperate with court proceedings. When Vann refused to respond, and only stared blankly at Lake County Superior Court Judge Kathleen Sullivan, she ended the hearing and told Vann he would stay in jail for the rest of his life until he cooperated so the hearing could take place.

When he returned to court Wednesday, his hands and feet shackled, Vann politely responded to each of Sullivan’s questions, in most cases simply saying, “Yes ma’am.”

Vann showed no emotion as the judge explained he could be locked up for the rest of his life, or put to death, if he’s convicted of killing either Jones or Hardy.

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Anith Jones and Afrikka Hardy have been identified as two of seven women whose bodies were discovered in northwest Indiana over the weekend. Police said a suspect being questioned in the deaths led them to the bodies. (Credit: Gary Police/Facebook)

Anith Jones and Afrikka Hardy have been identified as two of seven women whose bodies were discovered in northwest Indiana over the weekend. Police said a suspect being questioned in the deaths led them to the bodies. (Credit: Gary Police/Facebook)

His attorney entered a preliminary plea of not guilty, and said Vann was invoking his Fifth Amendment right against self-incrimination.

In addition to Hardy and Jones, police said he’s suspected of killing 36-year-old Kristine Williams, 28-year-old Teaira Batey, and three unidentified women whose bodies were found in Gary earlier this month.

Teaira Batey (photo provided)

Teaira Batey (photo provided)

Police have said Vann suggested he killed other women, but so far searches of hundreds of vacant buildings in northwest Indiana and Chicago’s southern suburbs have turned up no other victims.

The FBI has been assisting with the investigation, and has said it is looking into Vann’s claims he killed women in other states. Police have said he claimed his crimes date back as long as 20 years.

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Kristine Williams (Family Photo)

Kristine Williams (Family Photo)

Vann was in the U.S. Marine Corps from November 1991 to September 1993, when he received an “other than honorable discharge” for “minor disciplinary infractions.” He was based at Cherry Point Air Station on the coast of North Carolina. Police in Havelock, North Carolina, have said they are looking at Vann as a possible suspect in an unsolved murder from 22 years ago. Camille Whalen was 25 – a hitchhiker – her body dumped near a baseball field in August 1992. The autopsy said she was strangled and stabbed.