Talkleft blogs on the allarming practice of police attempting to get search warrants for people’s homes based upon samples taken from thier doorknobs:

Is it my imagination or are our Fourth Amendment protections shrinking? A U.S. District Court in Utah is considering a challenge to searches of the doorknobs to our homes. It’s a tactic being used around the country and it’s called the Ionscan test. Police swipe a doorknob with a drug-detecting cloth and if the cloth then tests postive for microscopic particles of a controlled substance, they tell a judge they have probable cause to get a search warrant. Do they? It’s up in the air right now.

I am reminded, in this case, of U.S. v. $30,060 (1994):

On November 8, 1994, the U.S. Court of Appeals for the Ninth Circuit again took the lead in asset forfeiture reform by putting dog alert evidence into its proper perspective.

For the past ten years, the lure of asset forfeiture revenue has prompted law enforcement officers to use dog sniffs as witch- hunting tools to seize cash — any amount of cash — without any other evidence of criminal behavior. So called “drug-sniffing dogs” are supposedly trained to alert to the smell of drugs on money, and their noses, police claim, are so sensitive that they can detect miniscule amounts of drugs. When dogs “alert” to cash, the officers claim that proves that the money has come into contact with drugs, therefore, the money is drug proceeds, and the person whose money was seized is a drug courier. FEAR has long pointed out the falacy of this argument — the dog’s alert may prove there is drug residue on some of the cash, but that proves nothing about the person from whom the money was seized.

In United States v. $30,060, the Ninth Circuit held that a drug dog alert has little probative value in showing that cash was connected to drug trafficking.

The court recognized the fact that “cocaine can be easily transferred simply by shaking hands with someone who has handled the drug: a pharmacist, toxicologist, police officer, or drug trafficker” (quoting Andrew Schneider & Mary Pat Flaherty’s Presumed Guilty series for the Pittsburgh Press, August 1991.) A dollar bill used to snort cocaine goes back into circulation, contaminating all the other bills it comes into contact with — in wallets and cash drawers, the court explained.

The court’s opinion cited reports showing that 75% to 90% of all circulated currency in Los Angeles (the city where the seizure occurred) is contaminated with cocaine residue.

Orin Kerr also has an interesting analysis of this case.