Here is Orin Kerr's analysis of Posner's opinion: http://volokh.com/2012/02/29/judge-posner-on-searching-a-cell-phone-incident-to-arrest/ http://volokh.com/2012

Here is Orin Kerr's analysis of Posner's opinion: http://volokh.com/2012/02/29/judge-posner-on-searching-a-cell-phone-incident-to-arrest/ http://volokh.com/2012/02/29/judge-posner-on-searching-a-cel... Posner's opinion is strange. Robinson (the main precedent) held that the 4th amendment permits the police to search any property on a person incident to arrest. The tension is that the case is almost 40 years old, well before cell phones, or any other technology that let someone carry around every detail of their life with something the size of a pad of paper. So one side (the government) says: "Robinson is clear. We can search the phone." The other side says: "No, cell phones are different. We need a precedent that makes sense in the 21st century." This binary can-search/can't-search is the "bright line" rule Kerr talks about. Posner comes out of left field and argues as if it's some kind of sliding scale. NEW RULE. Robinson is only about property on the arrestee. There are other cases about property in the car but not on the arrestee, e.g., Gant. Both Gant and Robinson have give really clear rules, and Posner does a good job muddling it all up. It's sort of funny coming from a so-called "law and economics" guy -- you'd think all else being equal, you'd prefer opinions with clear rules so as to lower the costs of administration. As I understand it, Orin's position is that cell phones are like cars (so Gant is controlling), not like cigarette containers (so Robinson is controlling). Gant says that police can search your car incident to an arrest if they believe it contains evidence of the crime for which you were arrested. Applying that rule is a principled way to avoid the problem with Robinson and cell phones, i.e., you get arrested for speeding and the police download your whole browser history.