He told authorities in a videotaped confession he rear-ended Morton's car on an exit ramp, then abducted her and killed her because he feared he would be sent back to prison.
Missouri on Tuesday put to death a man convicted of murdering a 19-year-old woman he encountered in a traffic accident in 2001, in the first execution in the United States since the Supreme Court upheld the use of a lethal injection drug.
David Zink, 55, was pronounced dead at 7:41 p.m. CDT after receiving a fatal dose of drugs at a state prison, said Mike O'Connell, spokesman for the Missouri Department of Corrections.
"David Zink callously took a young woman's life, and it is fitting he pay by losing his own," Missouri Attorney General Chris Koster said in a statement.
The U.S. Supreme Court ruled on June 29 that a drug used in lethal injections by Oklahoma, midazolam, did not violate the U.S. Constitution's ban on cruel and unusual punishment.
The high court did not directly address the constitutionality of the death penalty in the United States, but the issue provoked a caustic debate among the justices.
Zink, who was the fifth person executed in Missouri in 2015, was convicted of killing Amanda Morton of Strafford, Missouri.
Police found Morton's body in a cemetery. She had been strangled, her neck had been broken and her spinal cord sliced with a knife, according to court records.
Zink had previously been imprisoned for abducting and raping a woman. He told authorities in a videotaped confession he rear-ended Morton's car on an exit ramp, then abducted her and killed her because he feared he would be sent back to prison.
In a final statement released by the corrections department, Zink apologized to Morton's family and friends for his actions.
"I hope my execution brings them the peace and satisfaction they seek," he said.
The Supreme Court on Tuesday denied several appeals from Zink's lawyers to halt his execution, including claims that Missouri officials would be violating federal law by using pentobarbital obtained from a compounding pharmacy.
Zink had been the named plaintiff in a lawsuit brought by a group of Missouri death row inmates who allege the state's lethal-injection protocol is unconstitutional and creates a substantial risk of severe pain.
The allegations are part of a national debate about the use of compounded drugs in U.S. executions amid a shortage of traditionally used pharmaceuticals.