Here is an interesting article from Akron Ohio about a sexual relationship between a female officer and her informant. What is interesting about this case is that by the account given the agency seem to have had in place policy that would have mitigated the risk of this occurring. ALL contacts had to be reported and two handlers always present.
Confidential informants and police corruption
Here is a story from New Albany, Indiana about a police officer that went well and truly down the wrong road with a confidential informant, (human source, CHIS). This type of think could have happened in many police departments. The case is far from unique. No doubt everyone is seeking to cast all the blame on the officer. Time would be better spent looking at how this behaviour occurred and how it continued for two years.