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MILWAUKEE, WI – A Milwaukee fertility doctor is accused in a lawsuit of secretly using his own sperm to impregnate a patient in the 1980s, leading to a decades-later discovery that has triggered legal action and renewed scrutiny of fertility practices. The complaint, filed in Milwaukee Circuit Court, alleges Dr. Frederick Dettmann misled a woman into believing her donor was an anonymous medical student when he was, in fact, the biological father.

Mary Ellen Lukezich and her son, Joseph Laedtke Heider, brought the lawsuit Thursday, naming Dettmann along with the Wisconsin Health Care Liability Insurance Plan and ABC Insurance Co. as defendants. The case centers on allegations that Lukezich was deceived during treatment at Dettmann’s clinic and that the truth only surfaced after a consumer DNA test revealed Heider’s parentage.

Discovery through DNA testing

Heider, now in his 40s, learned in 2024 that Dettmann was his biological father after submitting his DNA to Ancestry.com, according to the lawsuit obtained by WISN. The filing claims Lukezich had been told at the time of treatment that the sperm donor was a “healthy young medical student” who wished to remain anonymous.

At a June press conference attended by WISN, Heider described the moment he learned the truth. “The anonymous medical student donor that my mother was promised as my biological father never existed. Instead, the DNA led back to one person. Dr. Frederick Dettmann, the very doctor my mom trusted to help her have a child,” Heider said. “Words cannot fully express what it feels like to learn that your entire identity is built on a lie.”

The lawsuit alleges that Lukezich sought treatment at Dettmann’s clinic during a time when fertility patients relied heavily on physician guidance and representations about donor identity and medical background.

Legal claims and response

Attorney Al Foeckler, representing Lukezich and Heider, said the case reflects a breach of trust at a vulnerable moment for patients seeking to build families. “These families come to fertility doctors at their most hopeful and their most helpless time. Trusting completely in the physician who holds their dreams of parenthood in their hands,” Foeckler told reporters. “Dr. Frederick Dettmann preyed on that desperation. He exploited that trust.”

Dettmann, now 91 and retired, denied the allegations in a statement provided by his attorneys to local media. “The events referenced are alleged to have occurred almost 50 years ago,” the statement said. “Dr. Dettmann has no independent recollection of the individuals making these allegations and is unaware of any evidence supporting the claims being asserted.”

The lawsuit seeks damages and accountability, raising questions about historical oversight in fertility medicine and the long-term impact on families who relied on representations made by physicians decades ago.

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