Gary Karr, 52, was charged with extortion and kidnapping and could face a sentence of life in prison. O'Hair, her son Jon Garth Murray and her granddaughter Robin Murray O'Hair disappeared from San Antonio in 1995 along with $500,000 in gold coins.
Although federal prosecutors named two other suspects, Karr was the only one charged.
The decision caps a two-week long trial that saw testimony from 68 witnesses, four of whom appeared for the defense. Karr did not take the stand.
Although he was found innocent ofof involvement in the actual kidnapping, he was convicted ofconspiracy in the robbery and extortion of the family for money.
The eight-man, four-woman jury began its deliberations Tuesday.
Jurors had to grapple with a small mountainof evidence, as they mulled five separate charges lodged against Karrin connection with the abduction and robbery of the O'Hairs.
Chargesincluded conspiracy to kidnap the O'Hairs; conspiracy to commitrobbery and extortion of the family's property; traveling interstateto commit violent acts resulting in the death of a person; conspiracyto profit financially from criminal acts; and transportation of stolenproperty across state lines.
The Murray O'Hairs are presumed dead, although their bodies have notbeen located, and no one has been charged with their murder.
Earlier Friday, jurors informed Judge Sam Sparks that theywere unable to reach unanimous agreement on all of the indictmentcounts. The judge ordered them to return to their deliberations, andthe final decision came minutes later.
Madalyn O'Hair and her family disappeared from San Antonio in 1995along with $500,000 in gold coins. Some at the time advanced theoriesthat she may have suffered from a terminal illness, or that the familyhad deliberately absconded with money from an atheist group.
Federalinvestigators, though, pieced together a tapestry of evidenceindicating that the O'Hairs were kidnapped, robbed and then killed.Their bodies are believed to have been dismembered and put into55-gallon drums and then buried, according to those close to the case.