An official website of the United States government
Here's how you know
A .mil website belongs to an official U.S. Department of Defense organization in the United States.
A lock (lock ) or https:// means you’ve safely connected to the .mil website. Share sensitive information only on official, secure websites.

The murder of Capt. Marty Theer

  • Published
  • By Dr. Deborah Kidwell
  • OSI Command Historian

Capt. Frank “Marty” Theer and his wife Michelle were high school sweethearts who had been married since Marty’s 1991 graduation from the U.S. Air Force Academy. Michelle worked for a psychologist and was studying to gain her own practical counseling license, while Marty completed a series of overseas assignments. Even though life seemed promising, trouble brewed on the horizon and the two struggled to keep their marriage alive. By December of 2000, Marty was dead, killed by an assassin’s bullet in the stairwell of his wife’s office building.

Prior to the murder, Michelle and Marty attempted marriage counseling, but it seemed they were hopelessly incompatible. Michelle wanted to go out in the evenings, while Marty preferred to stay at home, they told their psychologist. In most aspects, they seemed to be exact opposites, and it was later discovered that Michelle had a series of extramarital affairs, including one with an Army staff sergeant named John Diamond.

Michelle met Diamond in an online chat room and the pair decided to meet in person. Michelle and Diamond experienced an immediate strong connection and attraction. Even though both were married to other people, the pair had an affair and reportedly attended “swinger” parties, where couples traded partners for the purposes of having sexual relations in various one-night stands.      

The initial investigation quickly indicated that SSG Diamond, with whom Michelle had continued an on-again, off-again intimate relationship, even after briefly reconciling with her husband, was the most likely suspect. Diamond borrowed a gun similar to the murder weapon shortly before the murder and had no credible alibi for the time in question.

Diamond’s Courts Martial began in March 2001. When Michelle was called to the stand as a witness, she refused to answer questions under Fifth Amendment protections (the grounds that it might incriminate her). Nevertheless, Diamond was swiftly convicted and sentenced to life in Fort Leavenworth military prison and a reduction in rank to private.

While investigators believed that Michelle had taken part in the planning and perhaps execution of her husband’s murder, only civilian law enforcement had the authority to bring charges against her. With the investigation still ongoing, Michelle Theer fled the jurisdiction and took steps to ensure she would never be found.

Michelle had consulted a number of publications that described various tools fugitives could use to evade capture. She used computer software to create multiple identity documents, changed her hair color and changed her appearance through plastic surgery. Finally, in May 2002, a grand jury indicted Michelle Theer for murder, but she was nowhere to be found. Eventually, local authorities enlisted the U.S. Marshall Service in locating her, and she stood trial in 2004. 

After presentation of the evidence, a jury spent only a few hours deliberation before convicting, and the court later sentenced her to life in prison. Although Theer penned an internet blog proclaiming her innocence until 2012, and also filed numerous appeals, none have been granted. 

This case illustrates a number of challenges law enforcement must face throughout the life of successful cases. It is rarely straightforward and simple. This case took time to resolve, and agents often took a back seat to other investigative agencies and local officials while remaining involved until justice was served for an Air Force member.

Agents dug deep into the sordid sex life of numerous individuals to uncover the truth about the two murderers, and sorted through many he-said, she-said disagreements in the evidence. This case also illustrates the negative psychological environment that agents must endure in order to bring cases to conclusion. Even though the murder took place four years prior to the conviction, OSI’s Special Agents continued to provide investigative and other support until the proper authorities brought the case to a successful close.