It's a simple scenario, which happens more often than people realize. A man and a woman live together and are in love. The man enjoys smoking marijuana or using some other drug. Maybe he even grows his own plants or maybe he sells it too. Of course, the woman partakes as well, and she might even help take care of the plants or serve customers when the man is not around. The man does something to greatly anger the woman, such as cheating on her. Suddenly, the woman is no longer cool with her now ex-boyfriend's hobby or business.
So what if she used to smoke and sell his weed and help tend to his plants? She is going to get revenge by calling the police, and she certainly isn't going to tell the police that she was involved in any way. And the police are not about to charge her, when she was kind enough to hand over a drug dealer they otherwise would not have caught, even thought the police know damn well that the informant was probably with the suspect in the first place for the free drugs.
Believe it or not, most judges will find that the police have probable cause to get a search warrant, based upon information provided to them by an angry x-girlfriend or estranged wife. This is because the source of the information is known, and if the tip turns out to be false, there could be repercussions against the informant, such as a charge of false reports to law enforcement. Thus, the source of the information is deemed to be reliable enough to establish probable cause for a search warrant. Sure, suspect can claim that his vengeful ex planted the drugs, but that is an argument to be made if the case goes to trial. It is not going to stop the police from getting a search warrant and turning his life upside down.
Very few people are spiteful enough to run to the police and tell them about their ex's stash, but I have seen it happen. I think one of the reasons it is so rare is because the typical, angry girlfriend, who may be tempted to call the police, used drugs throughout the relationship herself, and will continue to do so after the relationship ends. Not only should those who live in glass houses should not throw stones, but the couple's mutual friends would be outraged, and naturally take the side of the "vicitm." Another reason is simple pragmatics. If the couple has children or the husband makes a lot more money than the wife, the woman has a vested, financial interest in her ex not getting in trouble, no matter how much she despises him. She is not getting child support, spousal support or alimony if her ex loses his job or is sitting in jail. Yet nevertheless, sometimes William Congreve's famous line rings true: "Heaven has no rage like love to hatred turned, Nor hell a fury like a woman scorned."
Matt McClenahen is a criminal defense attorney in State College, PA, with extensive experience in drug cases. http://www.mattmlaw.com/Criminal-Defense-Overview/Drug-Felonies.shtml