Where an expert’s testimony is substantially based upon a piece of evidence that was barred from being admitted, if the details of the expert’s testimony are contested and central to the case, the other party must be permitted to cross-examine the expert witness on the evidence on which they based their conclusion.The 1st District Appellate Court reversed and remanded a decision from Cook County Circuit Judge Thomas J. Lipscomb.Scott Gilman drove over one of the feet of Sweta Karn making a left turn at a …