In December 2024, Joseph Laedtke discovered he had nine half-siblings through an ancestry DNA test, all linking back to his mother’s former doctor. Mary Ellen Lukezich and her late husband, Thomas Laedtke, consulted Dr. Frederick Dettmann in the early 1980s due to fertility issues. They eventually agreed to use donor sperm for artificial insemination, with Dettmann suggesting a medical student from out of state as the donor.
Lukezich believed the donor choice matched her and her husband’s appearance. “I was young and just wanted to be a mom,” she shared. “I followed what he advised.” The couple kept the donor sperm decision private. “It was our personal matter. I got pregnant, and everyone was happy,” Lukezich said. Yet, further attempts to conceive were unsuccessful.
It was only through her son’s DNA test results that Lukezich learned Dettmann might have used his own sperm. Laedtke, now 43, did not expect remarkable results when he submitted his DNA in November 2024. “I received an email from Ancestry, revealing a half-sister,” he recalled. This led to the discovery of several other half-siblings.
Upon hearing the news, Laedtke contacted his mother, learning about the donor sperm for the first time. Lukezich was stunned to hear from her son that Dettmann was the likely donor. Laedtke utilized Ancestry’s genealogy tools to connect the dots, leaving his mother in shock.
While confronted with the truth, Laedtke longed for his deceased father, who passed away in 2005. As the reality of the situation became clear, he felt “disgust and disappointment.” He expressed a desire to hold Dettmann accountable for betraying his mother’s trust. Lukezich described the revelation as violating. “I feel like I’ve been violated,” she said. “Others should feel comfortable coming forward.”
The family’s attorney, Al Foeckler, confirmed multiple women have shared unsettling encounters with Dettmann since the story went public. “This man appeared to be a serial predator,” Foeckler stated. Dettmann, now 91, retired in the 1990s and resides in Arizona.
Dettmann’s lawyer did not respond to requests for comment. In a statement to the Milwaukee Journal Sentinel, attorney Sean Gaynor mentioned Dettmann’s awareness of the accusations but his inability to comment due to privacy laws. Gaynor also argued the alleged events occurred nearly 50 years ago, and Dettmann has no recollection of the individuals making the allegations.
In 1985, a report claimed Dettmann assaulted a woman during a gynecological exam, according to Wisconsin’s Whitefish Bay Police Department. Dettmann denied the accusation, and authorities opted not to pursue charges. Lack of evidence was cited as the reason. The victim’s name was redacted, and most documents were destroyed in line with record retention laws. No open investigation exists at present.
Police documents indicate the sexual assault complaint was reported to the medical board, which closed in 1986 after review. The Wisconsin Department of Safety and Professional Services reported no records of those complaints. Gaynor’s statement confirmed Dettmann was never sued, disciplined, or investigated professionally, and no ethical complaints were filed against him.