I hate to disagree but I am living proof that infrared devices used to discover large grows are admissible in a federal court ever since 911 you have no rights believe me I am paying the price with a class A felony now.
I am not allowed to get on an airplane along with half of my other privileges as a US citizen are gone it sux bad so do be careful.
Well, I am no lawyer, but the controlling case law for this issue can be found here:
http://www.law.cornell.edu/supct/html/99-8508.ZS.html
What this decision means is that infrared surveillance cannot be used as probable cause for a search warrant. If the police already have a warrant, or have other evidence of a grow, they can use infrared evidence to support their other techniques. Basically, infrared scans constitute as a "search" under the 4th amendment, so the police must show cause. I'm not saying that the cops can't use infrared, I'm saying they can't solely use it as the basis for a search warrant in court.
That's why I said its "usually not admissible". Because, if it is, that probably means that the cops already had enough dirt on you to justify to a judge that they should be allowed to use infrared.
What the cops
could do is use infrared, figure out you have a grow, then put you under physical surveillance, or monitor your electricity, or other things like that to gather more traditional evidence which can be used to secure a warrant.
However, as I said previously, I am highly doubtful that the police are going to be able to detect the heat from a 250 watt in a casual scan of the area. I can't imagine it would be able to raise the room temperature more than a few degrees, which would generally not be enough to provide any sort of conclusive lead as to whether or not something is growing in the house. Usually FLIR is only used to detect the heat signatures of commercial grows, which are difficult to hide. Quite frankly, an mid-sized air conditioner will probably vent more heat than a 250 watt lamp; 250 watts is not much bigger than some larger household fixtures.
As I said, I'd be much more worried about the smell, which is much easier to detect, than from the heat signature your house would generate on a helicopter mounted FLIR camera.
