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302 Cases Solved. Advancing justice for missing persons, unsolved homicides, unidentified and unclaimed remains.

Case Description

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Summary based on the NamUs case record (MP32841) and 7 other sources
Thomas Riha, a 39-year-old professor of Russian history at the University of Colorado, vanished from his Boulder, Colorado home on March 15, 1969. Born in Czechoslovakia, Riha was a naturalized U.S. citizen with a doctorate from Harvard who had also taught at the University of Chicago before joining the faculty at CU Boulder in 1967. He was known for being a meticulous and punctual individual. His disappearance was noted when he failed to appear for his classes. Upon entering his home, police found the breakfast table set, but the food was untouched. His personal belongings, including his shaving kit and clothing, were still in the house, and an open briefcase lay amidst scattered papers on his desk. The scene was one of disarray, which was uncharacteristic for the typically orderly professor.

The investigation into Riha's disappearance quickly became entangled with a mysterious woman named Galya Tannenbaum, who referred to herself as 'the Colonel'. Tannenbaum, who had a criminal record for forgery and embezzlement, claimed Riha was alive and well. After he went missing, she began to sell his property, including his car and house, and even donated some of his belongings to a museum. Forged documents transferring the title of Riha's house to Tannenbaum were discovered by police. The case took a darker turn as Tannenbaum was also a person of interest in two separate deaths by cyanide poisoning where she was named the beneficiary. When police searched her home in connection with the forgeries, they found Riha's passport and cyanide. She was arrested for forgery and committed to the Colorado State Hospital after pleading not guilty by reason of insanity.

The circumstances surrounding Thomas Riha's disappearance have fueled speculation for decades, with theories ranging from espionage to murder. His background as a Czech-American historian specializing in Russia during the Cold War led some to wonder about his potential involvement with intelligence agencies like the CIA or even the Russian government. Early in the investigation, the FBI and CIA were involved, with conflicting reports about Riha's well-being and whereabouts. Tannenbaum, before taking her own life with cyanide in the state hospital, gave conflicting accounts, at one point claiming to a fellow patient that she had killed Riha and disposed of his body, and at another point denying her involvement. Despite a U.S. Senate Intelligence Committee hearing and reported sightings that were never confirmed, no definitive answers have ever come to light. The case remains an unsolved mystery, leaving friends and family without closure.

Last Seen: Mar 15, 1969

Possible Unidentified Matches (6)

Unidentified remains cases whose details are consistent with this person, ranked by how closely they compare. Fields that are unknown in either case are left out of the score.

83%Moderate
John Doe — Boulder, Colorado
UP61119 • Found Jun 20, 1971
View case
Sex ✓Male
Age 100%Est. 38–52 vs 39 when missing
Race 100%White
Location 100%Same area, same county
TimingFound 2 years after last seen
Height 100%5'8"–5'10" vs 5'10"
Weight 77%170–180 lb vs 140 lb
Hair 100%Brown vs Brown
Eyes 0%Brown vs Blue
79%Possible
John Doe — Denver, Colorado - unidentified case UP7160
John Doe — Denver, Colorado
UP7160 • Found Apr 25, 1980
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Sex ✓Male
Age 100%Est. 40–50 vs 39 when missing
Race 100%White
Location 96%24 mi away, same state
TimingFound 11 years after last seen
Height 100%5'10" vs 5'10"
Weight 96%123 lb vs 140 lb
Hair 60%Black vs Brown
Eyes 0%Brown vs Blue
78%Possible
John Doe — Denver, Colorado - unidentified case UP7170
John Doe — Denver, Colorado
UP7170 • Found Sep 17, 1988
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Sex ✓Male
Age 92%Est. 60–70 vs 39 when missing
Race 100%White
Location 96%24 mi away, same state
TimingFound 20 years after last seen
Height 100%5'11" vs 5'10"
Weight 100%138 lb vs 140 lb
Hair 70%Gray vs Brown
Eyes 30%Hazel vs Blue
76%Possible
John Doe — Denver, Colorado - unidentified case UP13758
John Doe — Denver, Colorado
UP13758 • Found Nov 5, 1990
View case
Sex ✓Male
Age 100%Est. 30–40 vs 39 when missing
Race 100%White
Location 96%24 mi away, same state
TimingFound 22 years after last seen
Height 68%5'7" vs 5'10"
Weight 91%120 lb vs 140 lb
Hair 100%Brown vs Brown
Eyes 0%Brown vs Blue
76%Possible
John Doe — Cheyenne, Wyoming
UP131770 • Found Apr 11, 1977
View case
Sex ✓Male
Age 100%Est. 40–55 vs 39 when missing
Race 100%White
Location 80%81 mi away
TimingFound 8 years after last seen
Height 84%6'0" vs 5'10"
Weight 60%180 lb vs 140 lb
Hair 100%Brown vs Brown
75%Possible
John Doe — Denver, Colorado
UP7158 • Found May 21, 1979
View case
Sex ✓Male
Age 85%Est. 30–50 vs 39 when missing
Race 100%White
Location 96%24 mi away, same state
TimingFound 10 years after last seen
Height 68%5'7" vs 5'10"
Weight 87%117 lb vs 140 lb
Hair 60%Black vs Brown

These comparisons are generated automatically from public NamUs case data and are not confirmed identifications. Only DNA, dental or fingerprint comparison by investigators can confirm an identity. If you believe two cases are connected, contact the agency handling the unidentified case.

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