The 1991 Austin yogurt shop killings are an unsolved quadruple homicide which took place at an I Can't Believe It's Yogurt! shop in Austin, Texas, United States on Friday, December 6, 1991. The victims were four teenage girls: 13-year-old Amy Ayers, 17-year-old Eliza Thomas, 17-year-old Jennifer Harbison and Jennifer's 15-year-old sister Sarah. Jennifer and Eliza were employees of the shop, while Sarah and her friend Amy were in the shop to get a ride home with Jennifer after it closed at 11:00 pm. Approximately one hour before closing time, a man who had tried to hustle customers in his queue was permitted to use the toilet in back, took a very long time and may have jammed a rear door open. A couple who left the shop just before 11:00 pm, when Jennifer locked the front door to prevent more customers entering, reported seeing two men at a table acting furtively.

Around midnight, a police patrolman reported a fire in the shop, and first responders discovered the bodies of the girls inside. The victims had been shot in the head; at least one of them had been raped. A .22 and a .380 pistol were used to commit the murders, and the perpetrator probably exited out through a back door that was found unlocked. The organized method of operation, ability to control the victims, and destruction of evidence by arson pointed to an adult experienced in crime rather than teenagers, according to one of the original detectives on the case. Austin Police Department has DNA from an unknown male as a result of one of the rapes.^[1] A Y-chromosome match for the perpetrator DNA has been found in a research database of the Federal Bureau of Investigation (FBI) but it has declined to reveal the identity of the man in accordance with the law of anonymity for donors, and because thousands of men could bear this fragment of DNA, which is unable to identify individuals.

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Shortly before midnight on Friday, December 6, 1991, a patrolman from the Austin Police Department noticed a fire coming from an I Can't Believe It's Yogurt! shop and reported it to his dispatcher.^[2] After the fire was extinguished, firefighters discovered four nude bodies.^[2][3] Each had been shot in the head execution style with a .22 caliber lead bullet. Sarah's hands had been bound behind her with a pair of panties and she had also been gagged and raped. Jennifer was not bound but her hands were behind her back. Eliza had been gagged and her hands were also tied behind her back. All three had been severely charred and shot in the back of the head.^[4]

Unlike the others, Amy's body was found in a separate part of the shop. She was not charred but she had received second- and "very early" third-degree burns on 25–30% of her body. She was found with a "sock-like cloth" around her neck.^[5] She had been shot the same as the others; however, the bullet had missed her brain. She also had a second bullet which had caused severe damage to her brain, exiting through her lateral cheek and jawline.^[6]

Initial investigations had produced a large number of persons of interest, among them a 15-year-old caught with a .22 (not established to be the murder weapon) in a nearby mall days after the killings. Although he initially gave promising information, after tough questioning the detectives decided that he was trying to get himself out of the gun charge and eliminated him and three petty criminal friends whom he had implicated, none of whom were older than 17 at the time.^[7][8]

Several years later, a new detective on the case theorized that the four teens from 1991 were credible suspects. By that time, they were in their twenties. In a string of interrogations conducted by various detectives, confessions were obtained from some of the suspects. They said all four – Robert Springsteen, Michael Scott, Maurice Pierce, and Forrest Welborn^[9] – had participated in the murder.

No record was kept of what was said to the men in the 1991 interrogations, making it impossible to know whether the detectives had supplied information to the suspects in the initial interrogations. Such information could be used to implicate the suspects in later interrogations, if they were to reference it. Two of the four were sent to trial, entirely due to their self-incriminating statements. The prosecution went into great detail about the horrific nature of the crimes against the young victims, but presented no hard evidence other than the confessions. The two were convicted, one being sentenced to death and the other sentenced to life imprisonment because he had been 15 at the time. However, the prosecution's tactic of using excerpts of each one's alleged confessions at the other's trial was ruled to have violated the Confrontation Clause because the co-defendant was non-testifying. Both convictions were overturned on the Confrontation Clause alone, and the men were freed in 2009. The prosecution insisted they would be re-tried. However, forensic investigation showed that the DNA found in a victim was not theirs, nor was it that of the other two implicated in their confessions. The prosecution consequently abandoned plans for a retrial.^[10] Texas courts later decided that those released were not entitled to compensation as they had not proven they did not commit the crime.^[11]

One of the detectives in the interrogations, Hector Polanco, had been accused of coercing false confessions in a previous, notorious case involving exonerated defendants Christopher Ochoa and Richard Danziger. Both were released after 13 years in prison; Danziger was assaulted in prison which resulted in permanent brain damage.^{[12][13][14][15]}

Seven jurors from the trials have stated that they would not have convicted Scott and Springsteen had this evidence been available at the time.^[16][17]

At the time of the killings, a known serial killer, Kenneth McDuff, was in the area. He had a history of multiple murders involving teenagers, but was soon ruled out.^[18] He was executed on November 17, 1998.

The murders were the subject of Beverly Lowry's 2016 nonfiction book Who Killed These Girls? Cold Case: The Yogurt Shop Murders,^[36] Corey Mitchell's 2016 nonfiction book Murdered Innocents^[37] and the novel See How Small by Scott Blackwood.^[38]

• Lane Bryant shooting – 2008 mass shooting at a Lane Bryant store in the Chicago area
• Las Cruces bowling alley massacre – Similar unsolved crime in 1990
• Brown's Chicken massacre
• West Memphis Three

Murders in the Austin area:

• Murder of Jennifer Cave – Also in West Campus
• Murders of John Goosey and Stacy Barnett
• Celeste Beard