Dateline: Unmasking the Monster - Inside the horrifying sexual assault case of Dana Beatty

Dateline: Unmasking the Monster delves into a horrifying sexual assault case of Dana Beatty. Beatty was brutally assaulted by Frederick Louis Tanzer in 1989 in Cincinnati.

More than three decades later, Beatty's daughter Andra pushed the investigators to reopen the case in early 2024. Investigators were able to match DNA recovered from Beatty's home in 1989 with Tanzer's DNA obtained from a discarded coffee cup. According to the United States Attorney's Office, Tanzer was arrested in 2024. In September 2025, he pleaded guilty to three counts of false statements for lying to the FBI about his crimes. On January 28, 2026, he was sentenced to the statutory maximum of 15 years for lying to federal agents.

Unmasking the Monster is set to premiere on NBC at 9 PM ET on Friday, October 2.

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Dateline: Unmasking the Monster- What happened to Dana Beatty?

According to the United States Attorney's Office's press release, Dana Beatty (then Dana Sandbo) was sexually assaulted by physician Frederick Louis Tanzer. On August 1, 1989, Tanzer broke into Dana Beatty's condominium on Creighton Place in Cincinnati.

Tanzer, a medical doctor who practiced in Ohio, Colorado, and Kansas, was masked and dressed from head to toe in black Lycra (spandex). He carried a black gym bag with him. He sexually assaulted Dana Beatty for five and a half hours. He held a knife to Beatty's neck, dragged her to her bedroom, and blindfolded her with surgical tape. Tanzer tied her hands and feet to the bed frame and assaulted her multiple times. According to the court documents, Tanzer unplugged and disconnected the telephones.

However, the investigators were unable to crack the case for 35 years. According to the court documents, Dana Beatty described the assaulter as someone who was:

"white, with dark brown hair, approximately six feet tall with a thin or athletic build."

As per the Dateline episode, Beatty married a few years after the incident. A few years later, she and her husband welcomed their daughter, Andra. Andra was determined to bring justice for her mother. In early 2024, Andra contacted the Cincinnati Police Department and asked the investigators to reopen her mother's case.

Dateline: Unmasking the Monster - A breakthrough in Dana Beatty's sexual assault case

After Andra contacted the Cincinnati Police Department, a detective made a breakthrough. The evidence from the 1989 sexual assault case was preserved. With the advanced DNA technology, a detective was able to get a lead. When the investigators informed Dana Beatty about reopening the case, her daughter revealed that she pushed for it. According to the Lexington Herald Leader, Dana Beatty told Dateline,

"I was so blown away by her."

The investigators were able to match the DNA found from Dana Beatty's home with Tanzer's DNA that they obtained from a discarded coffee cup. Speaking about the breakthrough, Andra told Dateline,

"It was both a feeling of 'oh my gosh, I'm so grateful that we know' and also 'this makes things so much more complicated, and heavier, and way more messed up."

However, there was a legal catch. According to the press report, the statute of limitations for the crimes Tanzer committed during 1989 expired in 1995. Thus, Tanzer couldn't be charged with the sexual assault.

Dateline: Unmasking the Monster- Frederick Louis Tanzer convicted of lying to federal investigators

When Dana Beatty's case was reopened in 2024, the FBI, along with the Cincinnati Police Department, confirmed that the DNA found from Dana Beatty's home in 1989 matched Tanzer's DNA. When Tanzer was interrogated about the assault, he made several false statements. He denied having seen or interacting with Dana Beatty on the day of the attack.

Tanzer was arrested in 2024 and remained in custody. Since the statute of limitations for the crimes committed in 1989 expired in approximately 1995, he couldn't be charged with r*pe. In September 2025, Tanzer pleaded guilty to three counts of false statements for lying to the FBI. He admitted to tying up and sexually assaulting Dana Beatty in 1989. On January 28, 2026, the US District Court sentenced Tanzer to the statutory maximum of 15 years in prison. U.S. Attorney Dominick S. Gerace II said (via press report),

"Before admitting that he was the man who committed these horrific rapes in 1989, Tanzer lied to the FBI. His DNA confirmed his guilt, and evidence points to Tanzer being a serial rapist. Tanzer poses a grave risk to the public and deserves to be in prison not only for his lies but also for the despicable attack he was trying to cover up.”

Dateline: Unmasking the Monster - Dana Beatty sued Frederick Louis Tanzer

Even though Tanzer is serving his 15-year federal sentence, Dana Beatty told Dateline that in her mind the case is still unsolved and she is awaiting justice. She told Dateline that she had to seek therapy and suffered from anxiety, PTSD, chronic insomnia, and panic attacks. She further added that Tanzer needs to be held accountable for the heinous crime. She also continues to advocate for changes to the statute of limitations.

Dana Beatty sued Tanzer. Attorney Jeffrey Kenny told Cincinnati.com the lawsuit's ultimate goal was to have Tanzer undergo interrogation in a deposition and explain more about the crime he had committed.

Both Tanzer's former wife and current wife have accused him of drugging them before having intercourse with them. However, Tanzer was not charged in connection with those accusations.

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In the Dateline: Unmasking the Monster episode, Tanzer discussed the attack and how he developed a fantasy after he watched a sexually explicit movie at the age of 14.

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