People v. Marchan, 2019 WL 4915457 (App. Ct. Ill. 2019)

Defendant argues that the expert did not lay a foundation for her opinions because she did not provide specific details about the characteristics that led her to her conclusion. The court stated that he had properly explained in detail her methods and conclusions, and that Defendant had the opportunity to cross-examine her at length. Further, it is for the jury to decide the weight of the expert's testimony based on their credentials and basis for their opinion. The court also cites to precedent fingerprint case that an expert is not required to testify to the factual basis of their opinion to be admissible.Defendant also alleges ineffective assistance of counsel for failing to object to the expert's testimony, specifically that their opinion was "based upon a forensic certainty." The court holds that the defendant cannot satisfy either prong of the relevant test: (1) at the pre-trial hearing, the court only prevented testimony to a "scientific certainty" but allowed testimony based on training, experience, and background without limit on forensic certainty, and (2) defendant cannot establish that counsel's error prejudiced him because this was not the only evidence against him and her testimony would have only been limited, not excluded, under this standard.