6. Deterrence rationale
Modern constitutional criminal procedure includes three major "exclusionary rules." Only one of them is found in the actual text of the Constitution: the fifth amendment prohibition on compelling a person "to be a witness against himself", which excludes compelled confessions. The exclusionary rules appended to the fourth and sixth amendments are judicial creations. In the day-to-day operation of the criminal justice system, the fourth amendment exclusionary rule is the biggie. It dates only from 1961. As formulated by the Supreme Court, it requires all judges, state as well as federal, to "suppress" evidence that was illegally seized by police. (Suppression simply means that the evidence is concealed from the jury. The judges and lawyers pretend it never existed, and witnesses are instructed not to mention it.)
The Supreme Court has repeatedly told us that the suppression of evidence deters wrongdoing by police. Lower court judges accept this as fact for a very good reason: the Supreme Court says so. But the rest of us can be little more skeptical. Using the sabermetric principle that if a phenomenon exists, it must inevitably show up in the statistics, I looked for evidence that the judiciary's fourth amendment jurisprudence has had a deterrent effect.
My working hypothesis was that if the exclusionary rule has any overall tendency to deter police from making unconstitutional searches and seizures, the number of cases in which the legality of a search/seizure was challenged should have peaked relatively soon after 1961 and then gone into a steady decline. As more and more officers were deterred, it seems reasonable to suppose, ever-fewer would still need deterring.
Using Westlaw , I counted the number of cases in which the phrase "fourth amendment" appeared in the decisions of four major federal appeals courts at 10-year intervals beginning in 1952. The four courts were the Second Circuit (based in New York), Third Circuit (Philadelphia), Seventh Circuit (Chicago) and Ninth Circuit (California). I picked them because they're big courts and their borders haven't changed. Obviously, the search criterion was crude, and the completeness of the database influences the results; Westlaw includes some but probably not all unpublished opinions. Nonetheless, I think it's reasonable to assume that comparing the number of cases retrieved by the search reveals broad trends. The results:
Second Circuit
1952 = 0 cases
1962 = 4
1972 = 32
1982 = 25
1992 = 27
2002 = 36
Third Circuit
1952 = 0 cases
1962 = 3
1972 = 23
1982 = 13
1992 = 10
2002 = 57
Seventh Circuit
1952 = 1 case
1962 = 2
1972 = 24
1982 = 34
1992 = 61
2002 = 64
Ninth Circuit
1952 = 0 cases
1962 = 8
1972 = 36
1982 = 44
1992 = 207
2002 = 143
I think it can be confidently said that these numbers don't suggest a pronounced downward trend. If the fourth amendment exclusionary rule has a deterrent effect, it's not clear from the number of fourth amendment cases heard by the federal appeals courts.
Thursday, November 24, 2005 at 08:12PM in Exclusionary rule, Fourth amendment 
Reader Comments (4)
Of course, more broadly, using a search of "fourth amendment" in the circuit data is a very, very, very crude way to test your hypothesis (especially since 98% of crime is prosecuted in state courts).
One of the most troublesome confounding factors, I imagine, will be the behavior of prosecutors. If a fourth amendment case is decided by an appellate court, it means either that the trial judge thought the search was good (if it's a defense appeal), or else that prosecutors at both the trial and appellate level -- and, in the federal system, supervisors in Washington -- did. Only arguable cases get as far as an appeal.
Or, to put it another way, even if the cops aren't deterred from performing illegal searches, I know from personal experience that prosecutors are deterred from pursuing cases built on them. But I don't know how you would get an accurate read on how many cases are dropped before appeal.