Although an affidavit of a police officer familiar with the investigation is preferable, a hearsay certification from an assistant prosecutor may support probable cause to compel a defendant to submit to a buccal swab if it sets forth the basis for the prosecutor’s knowledge. Second, an affidavit or certification supporting probable cause to compel a buccal swab must establish a fair probability that defendant’s DNA will be found on the evidence. Here, the State failed to show probable cause.