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Attorneys for the man accused of killing Tennessee nursing student Holly Bobo argued Tuesday that investigators had arrested the wrong person and attempted to raise suspicions about a local sex offender known locally as "Chester the Molester."

Terry Dicus, the former lead investigator in the case for the Tennessee Bureau of Investigation (TBI), testified that he had ruled out Zachary Adams as a suspect shortly after Bobo disappeared in April 2011.

Instead, Dicus said, he had focused on Terry Britt, who has multiple convictions for sex offenses dating back to the 1970s and lived near the Bobo home in Decatur County, about 100 miles southwest of Nashville.

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Former Tennessee Bureau of Investigation criminal investigator Terry Dicus is questioned by Assistant District Attorney Paul Hagerman Tuesday. (Kenneth Cummings/The Jackson Sun)

"His alibi was garbage," Dicus said of Britt, who told investigators he and his wife were doing renovations on their home at the time of Holly's disappearance. The investigator said Britt claimed he and his wife had gone shopping for a new bathtub at a certain store, but employees could not remember seeing anyone who matched Britt's description that day.

Dicus added that Britt's voice was similar to a voice Holly's brother heard the morning of her disappearance and claimed that Britt may have changed his appearance after Holly vanished.

Dicus said he ruled out Adams as a suspect after cross-referencing pings from his and Holly's phones the morning of the disappearance.

"I’m trying to put together a puzzle," Dicus said. "If I find five pieces that don’t fit, I’m done. If I find two pieces, I’m done. It’s not this person. You may disagree with me that that wasn’t enough but all you really have to have is one fact that says this person couldn’t have kidnapped her and you need to go do something else."

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Holly Bobo vanished in 2011.

Investigators were suspicious enough of Britt to wiretap his phone and bug his house. Dicus added that cadaver dogs picked up scents of human decomposition near shovels, an ax and a hammer at Britt's home.

However, Dicus admitted that he didn't think all the dogs that searched Britt's home were accurate, and Britt was never arrested in connection with Bobo's disappearance.

Dicus was removed from the case in 2013. Bobo's remains were found in woods near her home in September 2014.

Under cross-examination, Dicus admitted that he was not aware of alleged statements by Adams that connected him to Bobo's disappearance. Acquaintances and friends of Adams — as well as fellow jail inmates — have testified that he made comments about harming Bobo.

Adams has pleaded not guilty to kidnapping, raping and killing Bobo. He faces the death penalty if convicted of first degree murder.

Adams' brother, John Dylan Adams, faces the same charges. His trial has not been set.

The Associated Press contributed to this report.