The court acquitted Richard Winfrey Sr., reversing his 2007 conviction in the murder of high school janitor Murray Burr in the small town of Coldspring, about 60 miles north of Houston.
Under the ruling, prosecutors will not be allowed to retry the case.
Winfrey remained in state prison Wednesday. His attorney, Shirley Baccus-Lobel, said she planned to immediately file a motion for his release with the state appeals court. It is possible he could be freed by Friday, his 57th birthday.
"We thank God first and then Shirley second," said Vicky Winfrey-Daffern, the defendant's sister. "We are so overjoyed. Everybody's turning flips."
The main evidence against Winfrey in the 2004 murder was a positive scent identification from three bloodhounds named Quincy, James Bond and Clue. The dogs belong to former Fort Bend Sheriff's Deputy Keith Pikett, who retired earlier this year after being targeted by the Innocence Project of Texas, a group that claims the ex-lawman passes off junk science as legitimate investigative techniques.
Pikett is a defendant in at least three lawsuits from men saying they were wrongly jailed after his dogs linked them to crimes they did not commit. He did not return a message left by The Associated Press.
Trained dogs are routinely at border checkpoints and airports to smell for drugs, bombs or other contraband. They're used by search and rescue teams and in other police work, such as to chase suspects.
In Winfrey's case and other Texas cases, however, Pikett's bloodhounds use a "scent lineup" to link defendants to crimes.
Three years after Burr's death, Pikett's dogs sniffed clothing worn by the murder victim when he was killed. Authorities then took scent swabs from six individuals and placed them in separate coffee cans. The dogs alerted Pikett when they sniffed the coffee can containing a swab taken from Winfrey, the deputy testified.
The appeals court ruled that "scent-discrimination lineups, when used alone or as primary evidence, are legally insufficient to support a conviction."
No eyewitnesses put Winfrey at the crime scene, and fingerprints, footprints and hairs were not a match to the defendant, according to court records. The scent ID was the primary evidence in the case.
"It cannot be denied that the jury and the court of appeals found the dog-scent lineup evidence in this case to be compelling," the appeals court wrote in its opinion.
"Hallelujah," said Baccus-Lobel, Winfrey's attorney, who praised the court for doing the "right thing."
The district attorney of San Jacinto County pointed out that Winfrey told police that he thought he was their top suspect at a time when authorities did not consider him one. A jailhouse snitch also testified that Winfrey told him about certain details of the crime, according to court records. The appeals court, however, did not find those points sufficient to uphold the conviction.
The DA, Bill Burnett, died earlier this year. The county's acting DA, Jonathan Petix, did not return a message left by the AP.
Jeff Blackburn, the chief counsel for the Innocence Project of Texas, has led the charge against dog scent identification and other types of "junk science" in Texas. He said he believes there are dozens of innocent people behind bars statewide because of similar dog scent cases.
"This puts out a strong message from the court about junk science in this state," Blackburn said. "This is really the first time the court has rejected the use of this junk."
Also prosecuted in the murder were Winfrey's children. His son, Richard Jr., was acquitted in 13 minutes. His daughter Megan, who was 16 at the time of the killing, was convicted of capital murder and conspiracy to commit capital murder and sentenced to life in prison.
Her appellate attorney, Scott Pawgan, said the ruling in the elder Winfrey's case could help free Megan Winfrey. Pikett's dogs also matched Megan's scent to the clothing word by Burr.
"I think this is voodoo science at its worst," Pawgan said. "It's scary that juries will rely on it to convict people."