Project Levitas was a military scientific project contracted by LuthorCorp with the goal of creating the ultimate interrogator. Exposing the interrogator with a gas (the ingredients of which included Green Kryptonite) would grant them an ability to compel anyone around them to tell the truth.
Lionel Luthor[]
Under Lionel Luthor, LuthorCorp became the civilian contractor for Project Levitas for the United States Army. The project was overseen by U.S. General, Dr. Jonah Doyle. They came to suspect that the gas would work, but Dr. Doyle found that the toxicity levels were too high. Ensuring that anyone exposed to the gas would be dead within days. Dr. Doyle developed an antidote, which was never tested at that time. Dr. Doyle shut down the project, not wanting to risk the life of any test subject. Lionel responded by arranging Dr. Doyle to get a dishonorabe discharge.
Lex Luthor[]
Some years later, Project Levitas was revived by Lex Luthor at LuthorCorp Fertilizer Plant Number Three in Smallville, without the knowledge or involvement of Lionel. Local teenager Chloe Sullivan was exposed to the gas, when she broke into the plant. She almost died, but Clark Kent was able to save her life with the help of Dr. Doyle's antidote. The revived project was shut down by Lionel Luthor.