At the November 22 symposium on the Supreme Court's treatment of DNA issues in Maryland v. King and Association for Molecular Pathology v. Myriad Genetics, there were some conflicting accounts about the state of Iowa's law on DNA testing of arrestees or people convicted of crimes. One presenter's slide indicated there was no such policy, while another presenter indicated that Iowa was going in a more permissive direction when it came to people convicted of misdemeanors.
After looking more into the issue, I found that Iowa's law is in an interesting state. Currently, Iowa's law requires that those who are convicted of felonies, who are determined to be sexual predators, and who are found not guilty by reason of insanity, among a few other categories. But that is going to change next year, as a recently-passed bill will require the collection of DNA samples from people who are convicted of misdemeanors.
While I don't think the Supreme Court has addressed the constitutionality of requiring DNA sample collection for those convicted of misdemeanors, this practice is most likely permissible, given the Court's ruling in Maryland v. King. While Maryland v. King held that DNA could be collected in situations involving serious offenses, the Court held that all the state needed to collect the DNA was probable cause to arrest and booking of the suspect. Because a central consideration of these cases is whether the suspect or defendant has a reasonable expectation of privacy, the misdemeanor conviction rule is probably permissible under King, since somebody who has been convicted, rather than simply arrested, has a lower expectation of privacy.