DALLAS (AP) — A Texas man who has spent more than 15 years in prison for kidnapping and robbery is expected to become the latest wrongly convicted person proved innocent by DNA testing, a prosecutor said Thursday.

Patrick Waller, 38, was convicted of aggravated kidnapping, aggravated robbery and cocaine possession in connection with a 1992 kidnapping and assault. DNA testing conducted last year excluded Waller as the contributor of DNA found at the crime scene, said Mike Ware, the head of the Conviction Integrity Unit in the Dallas County prosecutor's office.

The DNA testing proved a match to another man who Ware said has confessed to the crime and implicated an accomplice, who also confessed. Neither, however, can be prosecuted because the statute of limitations has expired. Both are free, although one is on parole, Ware said.

"It is a gross understatement to say that we are displeased with the fact that we cannot seek justice for the victims in this case because of the laws back in 1992," Dallas County District Attorney Craig Watkins said in a statement.

Telephone messages left for Waller's attorney were not immediately returned.

The abduction happened in March 1992, when two men kidnapped a couple and stole several hundred dollars. The men also sexually assaulted the woman after tying up the man, Ware said.

Another couple who drove up to the scene were also held at gunpoint. A security guard arrived and scared off the men, who fled in separate cars, Ware said.

Three of the four people abducted picked Waller in a photo lineup. The fourth later picked him out of a live lineup, Ware said.

Waller maintained his innocence and presented an alibi at trial but was convicted and sentenced to life in prison.

He had requested a post-conviction DNA testing in 2001 but was denied by a judge, Ware said.

"It was an appropriate case for testing in 2001," Ware said. "Had he been tested back then, then the actual perpetrator could have been identified and could have been prevented from paroling out."

Waller had better luck under Watkins, whose office works with the Innocence Project of Texas to review cases in which jailed inmates have requested DNA testing.

Counting Waller, DNA testing has proved the innocence of 19 Dallas County men since 2001, a national high, according to the Innocence Project, a New York-based legal center that specializes in overturning wrongful convictions. Texas leads the nation with 33 such exonerations.

A hearing for Waller is scheduled for next month in the state district court in Dallas.