Here is part two of the P-I's magnificent series on how police agencies sometimes extend a little "professional courtesy" to their colleagues on DUIs:
http://seattlepi.nwsource.com/specials/undueinfluence/326612_favors07.html
Pardon the repetition: How was it again that the P-I found this out: "For this project, Seattle P-I reporters sent public disclosure requests to more than 270 law enforcement agencies across Washington."