MOUNT PLEASANT, Iowa -- Skeletal remains discovered in southeastern Iowa in March are believed to be those of a 24-year-old mother who vanished last year, but how and why she died may be never known because a key suspect committed suicide, investigators said Wednesday.

Division of Criminal Investigation special agent Jeff Uhlmeyer said investigators were confident the remains are of Jackie Douthart, of Mount Pleasant, who disappeared a year ago Tuesday after a night out with friends.

Uhlmeyer said investigators have not unable to determine how Douthart died, but they believe foul play was involved. He said the person of interest in the case was a 24-year-old male acquaintance who was the last person with her early on May 22, 2011. The man, Benjamin Biggs of Mount Pleasant, shot himself to death last June during a police chase and standoff in which he shot and injured two officers in western Illinois.

Uhlmeyer said the identification was based on an examination by a forensic anthropologist, who determined they were consistent with a female of Douthart's age and height who died last summer or fall.

Family members also identified a ring, a wristwatch and fingernails discovered with the remains as belonging to Douthart.

Scientific testing has been unable to confirm her ID. The state crime lab could not develop a DNA profile to check against her DNA because the bones had been exposed outside for months before they were discovered, he said.

The remains will be sent to a laboratory for mitochondrial DNA testing, a process that could take a year and will try to link the remains to her mother's or daughter's DNA. A forensic odontologist also continues to try to link the remains to her through dental records.

Once testing is over, the remains could be released for burial.

Uhlmeyer said the investigation into Douthart's death would continue and urged anyone with information to come forward. But he also said investigators believed the deceased Biggs was the key person of interest after interviews and polygraph examinations ruled out several other potential suspects.

After he was questioned in the disappearance several times, Biggs stole a vehicle in Quincy, Ill. and led police on a high-speed chase. He drove into a police cruiser and shot an officer before crashing his car and fleeing on foot. Authorities say he barricaded himself in a house during a six-hour standoff in which he shot another officer before shooting himself in the head. Both officers were not seriously injured because they were wearing protective clothing, Uhlmeyer said.

Uhlmeyer said investigators presented the case to a cold case review unit in December, and "everyone involved clearly felt that we were in the correct path with the person that we zeroed in on." But he said the full story may never be known since Biggs and Douthart, who met days before her disappearance, are both dead.

Authorities had offered a $2,000 reward for information about Douthart's disappearance, and friends and family members used social media, flyers and even a psychic in their search for her. Douthart had tattooed Zoey on her ankle, the name of her daughter.

Douthart's family thanked investigators for professionalism as they "worked on answering our questions and finding Jackie." Uhlmeyer, the lead investigator, said the case presented "a large amount of stress and emotions" for everyone involved.

More than 150 leads had led them nowhere, he said, "other than the person we zeroed in on."

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