While a convicted rapist is on trial this week in Davenport, today Iowa Senator Chuck Grassley is learning more about the use of D-N-A evidence in such cases. Grassley is scheduled to take part in a subcommittee hearing about the use of D-N-A in sexual assault crimes. He says the purpose of the hearing is to find out the latest scientific evidence of how and when the D-N-A evidence should be used.Grassley, the ranking republican on the Senate’s Judiciary Subcommittee on Crime and Drugs, says many new uses for D-N-A technology have been found in the recent years. For example, it’s used more and more to find perpetrators of a crime. Grassley says it’s also used to find innocence for people who’ve been falsely accused of a crime.Trial opened Monday for Vinson Champ, the former “Star Search” comedian who’s accused in the 1997 rape of a student at St. Ambrose University in Davenport. The 40-year-old Champ has already been convicted of two rapes in Nebraska.