Woman finds out fertility doctor is her child's real father after he lied that donor was 'healthy young medical student,' bombshell lawsuit claims

By LAUREN ACTON-TAYLOR, US NEWS REPORTER Published: 05:08, 11 August 2026 | Updated: 05:11, 11 August 2026 A woman in Wisconsin is suing her fertility doctor after discovering he fathered her child instead of the 'healthy young medical school student' donor she was promised, a shocking lawsuit has claimed. Mary Ellen Lukezich, 71, was a patient of Dr Frederick Dettmann over 40 years ago when she was artificially inseminated with a donor's sperm.  Now, Lukezich and her son, 43-year-old Joseph Laedtke Heider, are suing Dettmenn, now 91, after they discovered Heider allegedly had nine other half-siblings fathered by the doctor, NBC reports. 'Words cannot fully express what it feels like to learn that your entire identity is built on a lie,' Heider said at a news conference in June, ABC-affiliate WISN reported.  In December 2024, Heider submitted his DNA to Ancestry.com and made the shocking revelation that Dettmann was his biological father, the lawsuit obtained by the outlet claimed.  'Upon tracing these DNA connections, Joseph identified a direct genetic link to Dr Dettmanns' family; that upon information and belief, this genetic information established that Dr Dettmann is Joseph's biological father,' the suit said.  Lukezich had been a patient of Dettmann's in 1982 and, after medication and surgical treatments proved unsuccessful, he recommended she try artificial insemination, the outlet reported.  According to the filing, Dettmann told her that the donor would be an anonymous 'healthy young medical school student.' Mary Ellen Lukezich, 71, and her son, 43-year-old Joseph Laedtke Heider, are suing Dr Frederick Dettmenn claiming that Heider had nine half-siblings fathered by the fertility doctor Lukezich was a patient of Dr Frederick Dettmann over 40 years ago when she was artificially inseminated with, what she believed was, the sperm of a student donor The lawsuit was filed on August 6 by their attorney Al Foeckler, seen above, with the Wisconsin Health Care Liability Insurance Plan and ABC Insurance Co also listed as defendants The lawsuit alleged that Dettmann, instead, used his own sperm during the procedure which led to the birth of her son, Joseph, the following year.  'The anonymous medical student donor that my mother was promised as my biological father never existed,' Heider said at the news conference.  'Instead, the DNA led back to one person. Doctor Frederick Dettmann, the very doctor my mom trusted to help her have a child. The lawsuit was filed on August 6 on behalf of the mother and son by their attorney Al Foeckler, with the Wisconsin Health Care Liability Insurance Plan and ABC Insurance Co also listed as defendants.  'These families come to fertility doctors at their most hopeful and their most helpless time,' Foeckler said, the outlet reported.  'Trusting completely in the physician who holds their dreams of parenthood in their hands. Dr Frederick Dettmann preyed on that desperation. He exploited that trust.' The since-retired doctor denied any wrongdoing in a statement submitted by his legal team on his behalf.  'The events referenced are alleged to have occurred almost 50 years ago. Dr Dettmann has no independent recollection of the individuals making these allegations and is unaware of any evidence supporting the claims being asserted,' the statement said, according to WISN. According to the filing, Dettmann told her that the donor would be an anonymous 'healthy young medical school student' The since-retired doctor denied any wrongdoing in a statement submitted by his legal team on his behalf According to Whitefish Bay police records, Dettmann had been accused of assaulting a woman during a genealogical exam in 1985, TMJ 4 reported.  No charges were issued, citing that proving the assault would be 'too difficult,' according to the outlet.  The Daily Mail reached out to Wisconsin Health Care Liability Insurance Plan and ABC Insurance Co. and attempted to reach Lukezich, Heider and Dettmann for comment.