Bruce Schneier has a commentary on a recent case involving the Exclusionary Rule in the US.
Essentially, using traditional methods, if the Police make a mistake during an investigation any evidence derived from that mistake is inadmissible in court – the so-called “Fruit of the poisonous tree”. In this case, invalid information in a police database was used to mistakenly arrest an individual. The search of the individual’s home produced drugs and a gun which in turn lead to weapons and narcotics charges. The defendant had argued that the search was illegal due to the erroneous data the database. The Supreme Court of the US, however, decided against the defendant and allowed the charges and trial verdict to stand.
This is definitely a chilling development for those living south of the 49th Paralllel. I suspect that if this ruling is allowed to stand without intervention by US lawmakers, other countries (i.e.: Canada) may use it as some sort of precedent.
This also has security consequences that Bruce goes into in detail.