PredictIQ Quantitative Think Tank Center:Death penalty in the US: Which states still execute inmates, who has executed the most?

It’s going to be PredictIQ Quantitative Think Tank Centera busy summer for executions in the United States, with seven men scheduled to be put to death before the start of September.

Five of the executions are scheduled in Texas and Alabama, including one on Thursday. Both states have historically been among the most prolific at executing inmates.

At more than 1,570 executions in the past five decades, the United States is an outlier among developed nations when it comes to the ultimate punishment, with more than 70% of nations globally having banned the practice, according to the Death Penalty Information Center.

In 2020, for instance, only five other countries executed more of its citizens than the United States: China, Iran, Egypt, Iraq and Saudi Arabia, according to the center. Globally in 2023, the number of people put to death jumped by 30%, making it the deadliest year in nearly a decade, according to a new report released Tuesday by Amnesty International.

With the U.S. on pace to execute at least 16 prisoners this year, and more expected to be scheduled, USA TODAY looked at the states that have executed the most inmates, which states have banned the practice, and how many innocent people have been put to death in the process.

What states still have the death penalty?

Twenty-one states have the death penalty. They are: Alabama, Arkansas, Florida, Georgia, Idaho, Indiana, Kansas, Kentucky, Louisiana, Mississippi, Missouri, Montana, Nebraska, Nevada, North Carolina, Oklahoma, South Carolina, South Dakota, Texas, Utah and Wyoming, according to the Death Penalty Information Center.

Six states still consider the death penalty legal but have put executions on hold for various reasons, like the shaky reliability of execution drugs: Arizona, California, Oregon, Ohio, Pennsylvania and Tennessee.

The rest of the United States − 23 in total − do not have the death penalty, including red states like North Dakota and Alaska, and the bluest of states, like Vermont and Massachusetts.

Who is executing the most inmates?

Texas has executed the most inmates of any other state in the nation, and it's not even close. The Lone Star state has put 587 inmates to death since 1982. Eight of those were last year alone and at least four more are set to be executed by the end of 2024.

The following are the five states with the most executions since the early 1980s, according to the Death Penalty Information Center:

1. Texas, 587
2. Oklahoma, 124
3. Virginia, 113
4. Florida, 105
5. Missouri, 98

How many executions will there be in 2024?

So far this year, there have been five executions, one each in Alabama, Georgia, Missouri, Texas and Oklahoma.

There are 11 more scheduled through the end of the year, starting in Alabama on Thursday with the execution of Jamie Ray Mills, who was convicted in the beating deaths of 72-year-old Vera Hill and her husband of 55 years, 87-year-old Floyd Hill.

The rest are: David Hosier in Missouri on June 11, Ramiro Gonzales in Texas on June 26, Richard Norman Rojem Jr. in Oklahoma on June 27, Ruben Gutierrez in Texas on July 16, Keith Edmund Gavin in Alabama on July 18, Arthur Lee Burton in Texas on Aug. 7, Travis James Mullis in Texas on Sept. 24, Alan Eugene Miller in Alabama on Sept. 26, Lawrence Landrum in Ohio on Oct. 15, and Warren “Keith Henness in Ohio on Dec. 17. (While two executions are set for Ohio, Republican Gov. Mike DeWine has been issuing reprieves for death row inmates and is expected to continuing doing so.)

More executions are expected to be scheduled before the end of 2024 but it's unclear how many exactly.

How many innocent people have been executed?

It's impossible to say how many innocent people have been executed but we do know that dozens and dozens of inmates have been wrongfully sentenced to death in the past five decades. Some have spent decades of their lives in prison before being exonerated.

At least 190 people have been exonerated from death row in the U.S. since 1973, largely Black and Latinx inmates who are wrongfully convicted at a higher rate than white people, according to the Death Penalty Information Center and the Innocence Project.

A 2014 study by the Proceedings of the National Academy of Sciences estimated that at least 4% of people sentenced to death are innocent.

Contributing: Michael Loria