- Driver was behaving erratically during the traffic stop.
- Driver was observed by the officer driving erratically.
- Driver was unresponsive / slow to respond during questioning.
- Driver appeared to be stoned out of his/her head.
- Etcetera...
The Supreme Court decision
Illinois v. Gates lowered the threshold of probable cause by ruling that a "substantial chance" or "fair probability" of criminal activity could establish probable cause. A better-than-even chance is not required.
Are those circumstances fact? To me that's seems like it would only warrant a sobriety test.
"Based on the decriminalization of one ounce or less of marijuana in 2011, the same court in
Commonwealth v. Cruz held that the smell of burnt marijuana no longer suggests criminal activity to justify the search of a car.
Although the smell of burnt marijuana can justify a field sobriety test, it does not justify the search of a car without cause. The judge concluded that the officers could not order the defendant out of the car based on smell alone. The odor of burnt marijuana "coupled with the driver's statement that he had been smoking earlier in the day" did not indicate cause to conduct a search."
Probable Cause to Seize Property
Probable cause to seize property exists when facts and circumstances known to the officer would lead a reasonable person to believe that the item is contraband, is stolen, or constitutes evidence of a crime.
When a search warrant is in play, police generally must search only for the items described in the warrant. However, any contraband or evidence of other crimes they come across may, for the most part, be seized as well.
Should evidence prove to have resulted from an illegal search, it becomes subject to the
"exclusionary rule" and cannot be used against the defendant in court. After hearing arguments from the prosecuting and defense attorneys, the judge decides whether evidence should be excluded.
http://criminal.findlaw.com/criminal-rights/probable-cause.html
Edittt: Now that I think of it, this may only pertain to decriminalized states. I think they're saying that an illegal amount can't be determined by smell. Therefore in decriminalized state like MA and RI smell is not enough probable cause for a search. This is just my interpretation and I could very well be wrong.