Texas inmate Robert Roberson, facing execution tonight, would be the sixth person put to death by the state of Texas this year.

Roberson, 57, was convicted of capital murder in 2003 for reportedly shaking his 2-year-old daughter, Nikki, to death. Advocates, his lawyers and a bipartisan group of lawmakers say he is innocent and the science behind “shaken baby syndrome” is flawed.

Texas legislators held a hearing Wednesday examining the evidence and hearing expert testimony in the case. Late in the evening, they voted unanimously to subpoena Roberson.

Here’s what to know about executions and death row in Texas:

What method does Texas use for executions?

Texas uses lethal injection — Pentobarbital — to carry out death sentences, according to the Texas Department of Criminal Justice website.

In Texas, from 1819 to 1923, people in Texas were put to death by hanging. In 1923, according to the Texas Department of Criminal Justice, the electric chair was adopted as the method, and made the state responsible for all executions. Before 1923, counties carried out death sentences.

Charles Reynolds was the first person in Texas to die in the electric chair on Feb. 8, 1924. Joseph Johnson was the last person put to death by electrocution in Texas, on July 30, 1964.

How many people are currently on death row in Texas?

The men are housed in the Polunsky Unit in Livingston in single cells with a window, according to the TDCJ website. The women are housed at the O’Daniel Unit in Gatesville.

Executions are carried out in Huntsville, about a three-hour drive from Dallas.

As of Wednesday, there were 174 people on death row in Texas, seven of whom are women, including Melissa Lucio who was convicted in 2008 of beating to death her 2-year-old daughter. In 2022, the Texas Court of Criminal Appeals granted a stay of execution so a lower court can review her claims that new evidence in her case would exonerate her.

Earlier this year, a district judge recommended the Texas Court of Criminal Appeals overturn her conviction after a South Texas district attorney’s office admitted prosecutors withheld evidence, the Texas Tribune reported.

When was the last execution in Texas and who was it?

The last execution in Texas was Oct. 2. Garcia Glenn White, 61, was pronounced dead at 6:56 p.m. following a chemical injection at the state penitentiary in Huntsville.

He was convicted of fatally stabbing twin 16-year-old girls. The bodies of Annette and Bernette Edwards. The bodies and their mother, Bonita Edwards, were found in their Houston apartment in December 1989. Authorities said he was later tied to the deaths of a grocery store owner and another woman.

How many people has Texas executed?

Texas leads U.S. states in executions since the death penalty was reinstated in 1976.

Currently 27 states, the federal government, and the U.S. military use the death penalty. Three states — California, Oregon, and Pennsylvania — also allow capital punishment but their governors have instituted a moratorium in those states.

Since Texas reinstated capital punishment and adopted lethal injection as its means of execution in 1977, the state has put 591 people to death, according to online records. Charlie Brooks was that first in that span. He was executed on Dec. 7, 1982 for the kidnap/murder of a Fort Worth auto mechanic.

From 1923-73, before the U.S. Supreme Court declared capital punishment “cruel and unusual,” Texas executed 506 people, according to TDCJ online records.

During that time, 69 people in Dallas County, 3 people in Collin County, 2 in Denton County, 6 in Ellis and 21 in Tarrant were sentenced to death.

What other executions are scheduled in Texas?

Two executions are scheduled for early 2025. Steven Lawayne Nelson, 37, is scheduled to be put to death Feb. 2, 2025. The Arlington man was convicted in the 2011 death of 28-year-old Rev. Clint Dobson at NorthPointe Baptist Church.

David Leonard Wood, who has been on death row since November 1992, is scheduled for execution on March 13, 2025. Wood, of El Paso, was convicted of killing one girl but was indicted in the deaths of five other girls found in the desert around El Paso between June and August 1987, according to the El Paso Times and TDCJ records.