NASHVILLE (AP) — A doctor says in a lawsuit challenging Tennessee's three-drug lethal injection protocol that a man executed last month experienced "torturous effects."

In the state Supreme Court filing Thursday, expert Dr. David Lubarsky concluded based on witness accounts that Billy Ray Irick would've felt like he was choking, drowning in his own fluids, suffocating, being buried alive and feeling a burning sensation. Irick was executed Aug. 9.

Lubarsky said Irick's hands were wrapped in tape and secured to a gurney, preventing the warden from observing hand movement, an indicator that someone isn't anesthetized.

Attorneys for death row inmates challenging the execution drugs also said officials didn't follow protocol because they didn't prepare a backup syringe of midazolam, the sedative.

State Department of Correction spokeswoman Neysa Taylor declined comment, citing ongoing litigation.