Actions in common law tort exist for both scenarios. Potential torts are negligence, trespass to chattel, and/or conversion.
Putting the largely apparent tort of negligence aside, since that is nearly always available when something and/or someone is damaged by another (requiring only the [negligent] act, causation and damages) I'll focus on the other tort potentially applicable to scenario 1.
The minority rule concerning trespass to chattel can be established even when the interference is negligent, whereas the majority rule requires intent to deprive. Interestingly, when the Restatement 2d of Torts talks about minority rule vs. majority rule, it really means "least often applied" vs. "most often applied", rather than merely "in some (fewer or greater) defined jurisdiction(s)".
With these type of uncommonly pled torts, you could find a huge jurisdiction like California having lower courts (especially small claims or district courts) applying both the minority rule in some courts and the majority rule in others. This, all within one judicial jurisdiction if that state's law court has not weighed in on their interpretation of preference.
The Restatement 2d (Second) of Torts § 217 and §218 define liability in trespass to chattel as "intentionally (negligently - minority rule ):
(a) dispossess(ing) the other of the chattel, or;
(b) the chattel is impaired as to its condition, quality, or value, or;
(c) the possessor is deprived of the use of the chattel for a substantial
(d) bodily harm is caused to the possessor, or harm is
caused to some person or thing in which the possessor has a legally
Trespass to chattel can consist of mere "intermeddling with or the limited use of the possession" and no damage need occur to the property, as damage is per se; however in your scenario, actual liability would occur in the destruction of the possession.
The 2nd scenario would lie in the more serious tort of conversion.
The tort of conversion will always requires intent to deprive the owner of his property, and the majority view is that the deprivation is intended to be total or forever (whether by continued deprivation or by destruction).
There are 3 elements required to establish conversion:
- plaintiff's ownership or right to possession of the property at the time of the alleged conversion;
- defendant's conversion by a wrongful act or disposition of plaintiff's property rights;
While anticipating the follow-up question to either scenario, being
"what about the fact that you didn't take the ball, but rather it ended up on your land, and shouldn't that count for something"...the answer (to the unasked question :~) is no.
The act of taking possession over property to satisfy the necessary prong in both torts may take any number of forms, but need not be wrongful to begin with. All that is required to establish possessory control over the chattel in a tortious manner is merely interfering with the plaintiff's right of possession, which is a wrongful deprivation of something the owner was entitled to possess (so in other words, even if you didn't go and take it, once you know it's there, it's not yours, and you seek to keep it, either temporarily, permanently – the act of wrongful possession has occurred. The way the property was acquired is not at issue.
Conversion and Trespass in Chattel are often spoken of interchangeably despite the fact that they are different. The difference between a cause of action for conversion and one for trespass against chattel is measured only by the degree of interference with the plaintiff's rights in their chattel.
While the distinction seems subtle in a vacuum, in the old English cases where these torts were typically decided, conversion was one small step from criminal activity, whereas today conversion may be the civil adjunct to a criminal suit.
*for those not familiar: chattel is any possession that is not real estate.