> Criminal law classifies strict liability as one of five possible mentes reae (mental states) that a defendant may have in pursuit of the crime. The other four are "acting knowingly," "acting purposely," "acting with recklessness," and "acting with negligence." The mens rea of strict liability typically results in more lenient punishments than the other four mentes reae. Typically in criminal law, the defendant's awareness of what he is doing would not negate a strict liability mens rea (for example, being in possession of drugs will typically result in criminal liability, regardless of whether the defendant knows that he is in possession of the drugs). [0]
Strict liability isn't about whether they can arrest you, it's about what they have to prove to convict you.
And, actually, I suspect that is a bad example and that a lot of drug laws are NOT strict liability. See: https://law.marquette.edu/facultyblog/2011/07/floridas-%E2%8...)
DUI/DWI, for example, is pretty universally strict liability, though. This leads to the occasional bizarre case where someone sleeping it off in their car gets charged and convicted for a DUI even though they weren't driving but were simply behind the wheel.
Off the top of my head I can't cite chapter and verse. The possession of drugs will almost certainly result in an arrest everywhere. However, most states where I have had contact with the legal system about this, good defense lawyers have lots of maneuvering room, and the court allows lots of mitigating circumstances (if they really aren't yours generally you have enough corroboration to limit the problem).
Possession of child pornography gets no such latitude.
Quite possibly arrested. However, a successful prosecution probably depends on the definition of "possession"--I suspect a competent defense attorney could argue that you really didn't take possession if you immediately reported it to the police and deleted it.
> Both are crimes where possession alone is cause for arrest.
Possession of drugs is not a "strict liability" crime.