I have heard as of one year ago that the police are no closer to solving this crime. It appears that traditional investigative techniques are unfruitful. Hence my thoughts.
This case can be solved by a union between the police and the prosecutors. It is now time to use the subpoena power, sworn testimony, and (if ncessary) immunized testimony. The police have chased down rumors, unsubstantiated hearsay and outright lies. There needs to be a concerted effort to establish the actual facts apart from barroom talk or campfire speculation. This is not an indictment against the police. They simply are up against a cunning quarry that is getting more comfortable as time passes. Through the collaboration of the police and prosecutors, this can be solved. I (and the police) have done this several times. A marriage between the police and the prosecutors can produce evidence from otherwise stonewalled witnesses. Potential witnesses can be given derivative use immunity if necessary. I have learned some techniques over the years and wish I could share it with the authorities in Iowa. However I cannot elaborate any further because the suspect may be monitoring this site.