The case was an early win for Governor Martin O'Malley: an expansion of Maryland's DNA database to include all arrestees, hoping to match suspects to unsolved cases. Alonzo Jay King of Salisbury challenged the law after his 2009 arrest for assault led to a conviction in a 2003 rape case. Last April the Court of Appeals said that the law violated the Fourth Amendment's ban on unreasonable search and seizure, and in July Supreme Court Chief Justice John Roberts allowed DNA collection to continue, at least until a decision was made. Maryland's Office of the Public Defender is challenging the case on King's behalf.
Oral arguments will be heard tomorrow.
Yvonne Wenger has an overview of the case in the Baltimore Sun, which includes the opinion of several prominent Marylanders. In another piece, she writes that the law actually expires this year and O'Malley wants state lawmakers to extend it.
Amy Howe of SCOTUSblog explains the legal arguments "in plain English." She writes that the Court's recent rejection of warrantless use of GPS tracking devices was not necessarily an indicator of how the justices will rule on Maryland v. King.
Over at Slate, Brandon L. Garrett and Erin Murphy argue that because way too little DNA evidence is collected at actual crime scenes, taking a DNA sample of each arrestee will not led to more solved cases--just more backlog.
Wikipedia entry on the Fourth Amendment.