A chemical engineering professor is set to testify about the ingredients in cigarettes today at Minnesota's tobacco trial. Minnesota public radio's Elizabeth Stawicki reports: The State's lead attorney is expected to call Channing Robertson--a Stanford University Chemical Engineering professor. Robertson has testified as an expert witness in a number of other trials including a southern California toxic waste case and lawsuits involving I-U-D birth control devices. Later in the week attorneys are expected to call to the stand Walker Merryman who directs the tobacco industry's public relations and lobbying group--The Tobacco Institute. Also set to testify--Bennett LeBow who heads Liggett tobacco Liggett has settled its case with the State of Minnesota but not