A Colorado dentist accused of fatally poisoning his wife in March pleaded not guilty Monday to charges of first-degree murder and tampering with evidence.

Authorities say James Toliver Craig allegedly poisoned his wife's protein shakes with arsenic he ordered online, after making a number of internet searches -- including "how to make poison" -- in the weeks leading up to her death.

Angela Craig, 43, died March 15 after being hospitalized several times for severe headaches and dizziness, according to the Aurora Police Department.

James Craig's trial is set for April 19, 2024, with a special panel for jury selection. Testimony likely will begin the following week. CNN has reached out to Craig's attorney, Andrew Ho, but did not immediately hear back.

In March, investigators alleged in an arrest warrant application, Craig "has shown the planning and intent to end his wife's life by searching for ways to kill someone undetected, providing her poisons that align with her hospitalized symptoms, and working on starting a new life" with another woman.

The affidavit says Angela Craig died after going to the hospital for the third time in March. After she arrived the final time, she had a severe seizure, was placed on a ventilator and was declared medically brain dead soon after, it says.

In the weeks before her death, James Craig used a computer at his dental practice to research multiple "undetectable poisons" and make internet searches including "how many grams of pure arsenic will kill a human" and YouTube searches for "how to make poison" and "Top 5 Undetectable Poisons That Show No Signs of Foul Play," according to the affidavit.

The husband also used a new email account to order arsenic online, the affidavit says.

According to the affidavit, Angela Craig's sister told investigators the couple's marriage was tumultuous and she was told by Angela that James Craig had previously drugged her because he was planning to attempt suicide and didn't want his wife to be able to stop him.

After Angela Craig's death, her sister told investigators James Craig told her he did not want an autopsy to take place.

"James said he felt if they couldn't figure out what was wrong with her when she was alive he wouldn't let them poke her more when she was dead," reads the affidavit.