Is this probable cause for search?

In the US, the police would need more evidence than a heat source to obtain a warrant to search.

A heat source could be a number of things with only one of them being the illegal growing of marijuana. Courts generally do not grant warrants unless there is a high probability of criminal activity.

If the house was known to be a drug house, or one of the residents was known to be a dealer, then the combined evidence *might* be enough for a judge to sign off on the search. But from a heat source alone would not be sufficient enough to issue a warrant.

In the United States, this alone would not be enough. The officer would need to go before a judge and ask for a Warrant to search the home. But a judge is unlikely to give you a warrant based on a large heat source in the home.

If this was the only factor, this wouldn't cut it. There are too many things that it could be. It might be a small electric heater, it could be a fire place, it might even be a workshop inside the home for welding or something. Heck it could even be a tanning bed. If you are asking for a search warrant, you need to be close to certain that you will find what you're looking for. A heat source doens't translate to growing marijuana every time.

Overflight with aircraft equipped with FLIR (forward looking infrared radar) are common however they are subject to certain restrictions depending upon the jurisdiction and circumstances. Minimum height restrictions apply as do a prohibition on targeting specific locations. If the police stay a certain amount of feet off the ground and do a random sweep of an area looking for heat signatures they can, in most cases, use the info to obtain a warrant or as part of the investigative process.

There are arguments that a case like that would set precedent for future situations. In reality, though, the police would still need a warrant before searching your residence. Probable cause is needed for a warrant. And in that case, the residency had previously been a known drug house of some sort, which combined with the heater gave them what they felt was reasonable cause for searching the premises.

Something like that probably wouldn't have gone over too well in the US, especially if no pot was found. If anything it would raise a red flag and they'd pull water and electric bills to look for unusually high activity before busting in to arrest your guinea pigs.

It is done in the US in the past and warrants have been granted for it.

The Supreme Court ruled that thermal scans can't be conducted without warrants:

http://www.wired.com/politics/law/news/2001/06/444...

The SCOTUS ruling basically says you can't use advanced technology to determine what is going on in a house without a warrant, so you need probable cause to obtain a warrant before you can even use technology to inspect a home from outside.

Right now, in the US, it depends on what Federal Appeals District you live in.

Different appeals courts have upheld or struck down fly over FLIR or other aerial information as enough for a warrant

None of the cases have gone to the supreme court yet for a final say so.

A case being heard bu SCOTUS right now may have impact. They are hearing arguments on whether the smell of marijuana adn the sound of flushing in response to a knock on the door is enough for a warrant-less entry.

why should the government care what people do? if they want to grow weed and smoke it then let them be. dont u think its rediculous there shootin infared signals in our houses to look for things like this? and bust in our doors?

I think Yes only if there had been some other suspicious activity at the residence-otherwise-NO