Pearson v. Callahan (No. 07-751) is a unanimous Supreme Court decision on 29 January 2009 authored by Justice Samuel Alito.
I found the facts implausible: A buyer of meth from an informant admitted to his home sued the police who searched his home without a warrant. The suit alleged law enforcement violated his 4th amendment freedom from unreasonable search and seizure.
The qualified immunity reasoning, and the loosening of the “Saucier” rule (Saucier v. Katz, 533 US 194 (2001) are difficult to understand. Therefore, I defer to the blog post of Georgetown University Law Center Professor Nancy Leong. In her commentary, she does not so much explain the decision as predict its impact upon future 4th Amendment cases involving the doctrine of “consent once removed”.
If you invite police informants into your home to see you buy drugs or commit other crimes, and you reside in a jurisdiction where it is not yet clearly established that the resulting search by law enforcement is unconstitutional – or you represent such people in court – then Pearson is the decision you need to read.