The first transgender person is executed in the US in Missouri.

In what is thought to be the first transgender person's execution in the US, a Missouri convict was executed on Tuesday for a murder committed in 2003.

Amber McLaughlin, 49, was found guilty of stalking, killing, and subsequently disposing of a former girlfriend's body close to the Mississippi River in St. Louis.

After being denied clemency, murderer Amber McLaughlin was put to death by lethal injection.

Early on Tuesday, Republican Governor Mike Parson rejected a clemency request, sealing McLaughlin's fate.

While receiving the pentobarbital injection that would prove deadly, McLaughlin spoke with a spiritual advisor by her side. A few minutes later, she was declared dead.

McLaughlin expressed contrition for her behavior in her final written statement. She said, "I'm sorry for what I did. I consider myself to be loving and caring."

Since the death penalty was revived in the middle of the 1970s, 1,558 persons have been put to death, according to a database on the website of the anti-execution Death Penalty Information Center. Except for 17, all of those executed were men.

The centre said there are no known previous cases of an openly transgender inmate being executed.

McLaughlin began transitioning about three years ago at the state prison in Potosi.

McLaughlin's difficult background and mental health issues, which the jury was never told about during her trial, were mentioned in the clemency appeal.

According to the petition, when she was a toddler, a foster provider put feces in her face and her adoptive father shocked her. It mentioned extreme depression that led to numerous attempts at suicide as a child and an adult.

The petition also contained records citing diagnoses of gender dysphoria, a disorder that results in suffering and other symptoms when a person's gender identity and the sex they were assigned at birth diverge.

However, according to her attorney Larry Komp, McLaughlin's sexual orientation was "not the main emphasis" of the clemency application.

Long before he transitioned, McLaughlin was dating Beverly Guenther in 2003. According to court documents, McLaughlin would frequently appear at Guenther's 45-year-old suburban St. Louis workplace after they broke up, sometimes hiding inside.

Guenther secured a restraining order, and occasionally after work, police officers would accompany her to her vehicle.

When Guenther didn't come home on the evening of November 20, 2003, her neighbors dialed 911. Officers arrived at the office building and discovered a blood trail and a broken knife handle close to her car.

A day later, McLaughlin directed police to the spot where the body had been discarded in St. Louis, close to the Mississippi River. Authorities claimed she had been repeatedly stabbed with a steak knife while being raped.

In 2006, McLaughlin was found guilty of first-degree murder. A jury couldn't agree on the punishment, so a judge executed McLaughlin. According to Komp, only Missouri and Indiana permit the death penalty to be imposed by a court.

A federal appeals court panel reinstated the death penalty in 2021 despite a 2016 court injunction for a new sentencing hearing.

“McLaughlin terrorised Ms Guenther in the final years of her life, but we hope her family and loved ones may finally have some peace,” Parson said in a written statement after the execution.