One of those was held at Bishop Leblond High School in St. Joseph to pray for Michael Taylor, the latest convict scheduled to be executed in the state.
"Killing people is wrong," said Jean Swymeler, who attended the vigil. "That's our main message."
For members of Missourians for Alternatives to the Death Penalty, this is starting to become a common occurance.
After a temporary stay was lifted in November, Missouri executed convicted murderer Joseph Paul Franklin. A month later Allen Nicklasson was executed. Just four weeks ago, it was Herbert Smulls. And now convicted murderer Michael Taylor is next in line.
Taylor and another man were found guilty of raping and murdering 15-year-old Ann Harrison in 1989.
MADP, along with other opponents, say secrecy surrounding the drugs used is inhumane.
"Part of the concern is there isn't enough research," said David Tushaus, an expert on capital punishment in the state. "We don't know how painful these drugs are."
The pharmecutical company that provided the drugs previously stopped supplying it for executions, meaning states like Missouri have to find alternative drugs.
"There is belief that Missouri is going across state lines to use a pharmacy from Oklahoma," Tushaus said.
In January, an Ohio man took ten minutes to die after one of these alternative drugs was unsuccessful.
"Many defense attorney's have said that that raises the question of cruel and unusual punishment," said Jonathan Turley, a law professor at George Washington University.
The United States Supreme Court could get involved in the case later this week.
But for now groups like MADP will rely on prayer.
Missouri State Senator Rob Schaaf spoke with KQ2 today about this issue. He believes that Missouri should be more transperent in disclosing what drugs they use and where they come from.