Four death row inmates filed a lawsuit in St. Louis on Wednesday claiming the drug injections Missouri is expected to use to execute them are unconstitutionally cruel.

The four convicted murderers filed a claim similar to one filed by convicted murderer Timothy Johnson, who argued last year that Missouri's method of execution created the possibility of a "painful and protracted death."

A federal judge dismissed Johnson's claim. Johnson, convicted of beating and kicking his wife to death in St. Louis in 1989, was executed Aug. 31.

Still, legal challenges to the lethal injections abound. The U.S. Supreme Court in January blocked the execution of a Florida inmate and agreed to consider his claims that his execution by injection could cause him excruciating pain.