A dentist accused of killing his wife by putting poison in her protein shakes asked a fellow jail inmate to plant letters to make it look like his wife was suicidal, police say.

James Craig asked the inmate to put the letters in Craig's garage and truck at his home, Aurora police detective Bobbi Olson testified Wednesday at a court hearing on the new allegation against Craig, KMGH-TV reported. The inmate believed the letters were written by Craig but meant to appear as if his wife, Angela Craig, had written them, said Olson, the lead detective in the case.

Angela Craig, a 43-year-old mother of six who was married to her husband for 23 years, died in March 2023 of poisoning from cyanide and tetrahydrozoline, the latter a substance found in over-the-counter eye drops, according to the coroner.

Craig is alleged to have bought poisons online just before his wife began to experience symptoms that doctors could not find a cause for. But his lawyers have argued there is no direct evidence that he put poison in his wife's shakes and have accused Olson of being biased against him.

According to Olson, Craig offered money to pay for the bond for the inmate to be released from jail or perform free dental work in exchange for planting the letters but the inmate decided not to take him up on the offer, the detective testified.

The inmate instead contacted law enforcement, she said.

The defense argued that the inmate was not a credible witness.

One of Craig's lawyers, Andrew Ho, pointed out that the inmate only contacted authorities after an initial hearing to review the evidence in the case last summer, which was widely covered by the media, and that the inmate could not accurately identify the color of Craig's truck.

However, a judge agreed prosecutors had presented enough evidence for Craig to also be tried on the new charge involving the inmate, filed last month, of solicitation to commit tampering with physical evidence. The inmate's name was redacted from the document.

"Is arsenic detectable in an autopsy?"   

Craig was already charged with first-degree murder and another count of solicitation to commit tampering with physical evidence. He pleaded not guilty to those two charges in November 2023.

Last July,  a police detective testified that Craig searched online for answers to questions such as "is arsenic detectable in an autopsy?" and "how to make murder look like a heart attack" a few weeks before she died.

Skye Lazaro, an attorney familiar with cases involving poison, told "48 Hours" contributor Natalie Morales that Craig's defense might argue that police rushed to arrest him. "It's essentially a three-day investigation," she said of the time it took police to charge him with his wife's murder.

According to a work bio and video posted online, Craig taught as an associate professor at the University of Missouri School of Dentistry for three years and has been practicing dentistry in the Aurora area since 2006.

Neighbors of the family told CBS Colorado they were stunned.

"I keep praying for the kids because they lost both parents at the same time," said neighbor Karen Lucero.

Craig is scheduled to face trial on Aug. 8.

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• Colorado
• Murder