If he was telling people you slept around and it is false, that is likely grounds for a defamation lawsuit. However, unless this man is very rich, not many attorneys will be interested in taking the case on without you paying their hourly fees. If he is rich or if you are willing to pay an hourly rate, click the "find a lawyer" tab and search for libel lawyers in Chicago.
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You can sue, but the better question is whether you can win, and if so, how much. It is probably not worthy it for you to file a lawsuit. You are better off putting your energies into collecting child support and related expenses and giving your child the best upbringing you can. Hopefully you have a lawyer helping you with the parentage case. Best wishes to you.
Defamation is defined as the publication of one or more false and unprivileged statements of fact to one or more third parties concerning an identifiable party, which harms that party's reputation.
A statement can be defamatory per se, where its meaning is apparent on its face and there is no need to prove actual harm (injury to reputation is presumed). A few examples here include words that prejudice a person or impute a lack of ability in a person’s profession, and words that impute a person has engaged in adultery or fornication. Assigning a monetary figure to presumed damages (mental suffering, harm to personal and professional reputation as well as standing in the community, economic loss, and personal humiliation) can be very difficult; it tends to be an inexact and arbitrary process.
Alternatively, the statement can be defamatory per quod; a plaintiff must plead and prove special damages to recover under that theory.
Some defenses to a defamatory statement include truth, consent, innocent construction, absolute privilege (e.g., a statement made in a judicial or legislative proceeding, or the police), opinion, and various statutory privileges.
False light invasion of privacy is a tort that is oftentimes pleaded alongside defamation (in the alternative).
Assuming you have one or more causes of action, whether or not it makes sense to proceed, financially and otherwise, is a decision that will need to be made. You would likely only find a defamation attorney who would work on an hourly basis (with security retainer) and, if the father does not have much in the way of non-exempt assets to satisfy any judgment you obtained, in part or in whole, you may not want to pursue the matter.
Hope this helps. Good luck.
Robert T. Kuehl
Kuehl Law, P.C.
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