1972 — The U.S. Supreme Court throws out all state death penalty laws, but capital punishment is later reinstated.
1983 — Illinois Gov. James Thompson signs a bill making Illinois the sixth state to use lethal injection.
1988 — Missouri Gov. John Ashcroft signs law allowing capital punishment by means of lethal gas or lethal injection at the discretion of the director of the Department of Corrections.
2000 — Illinois Gov. George Ryan halts all executions after 13 people condemned to death were found to have been wrongfully convicted.
2001 — Oklahoma City bomber Timothy McVeigh is executed at the U.S. penitentiary in Terre Haute, Ind. He is the first federal prisoner to be executed in 38 years.
2003 — Days before leaving office, Ryan grants clemency to all 167 death row inmates in Illinois, saying a flawed process led to the sentences.
2006 — A federal judge halts executions in Missouri, saying he is concerned that its current system poses unacceptable risk of pain.
2007 — Federal appeals judges in St. Louis let Missouri resume executions, finding there are sufficient safeguards to protect the condemned.
2007 — A Missouri law is enacted to protect the identities of current or former executioners and make it easier for them to seek civil damages if their names are exposed.
2007 — The U.S. Supreme Court agrees to hear arguments in a Kentucky death-penalty appeal in January, and state and lower federal courts nationwide halt all scheduled executions.
2008 — A lawyer for two Kentucky death row inmates tells the Supreme Court that lethal injection carries the potential to cause unnecessary and excruciating pain. Two justices say it might be better to send the case to lower courts to compare whether the process is riskier than a single, massive dose of barbiturate. A decision is expected later this year.