0. Trespass is a direct and focible injury (categoriy of tort). But is also a tort in its own right.

1. Trespass to the person may take the form of an actual battery of of a technical assault (this is coincident with the crime).
a) As a rule, the tort was actionable per se. But this has now changed: tresspass to the person is now confined to cases where the defendant acted intentionally (which the plaintiff must prove). If he can't establish this, the tort will be in neg- ligence, with the plaintiff bearing the onus of showing special damage. Next case and subsequent decisions:
Fowler v. Lanning 1959 - accidental shooting of a person.
b) Special tort: 'intentional injury' = indirect but foreseeable injury: Wilkinson v. Downtown 1897- a man telling a woman (jokingly) that her husband had been injured - she got a nervous shock.
Also: Janvier v. Sweeny 1919 - threat causing nervous shock (assault).
The rule was also applied in Khorasandjian v. Bush 1993 (nuisance).
c) See for more reference under 'assault' and 'battery'.

2. Trespass to land remains actionable per se. It is committed when one person enters upon land in the possession of another without laeful justification, or remains upon it after his authority to be upon it has been revoked. It may also be committed by merely throwing or putting things upon the land.
a) General rules
aa) The injury has to be direct and forcible:
River Ware Commissioners v. Adamson 1877 - car accidently going onto other's land - no trespass.
SMITH v. STONE (1647) - a man thrown on land by another committed no tresspass (he didn't intend it).
Rubbish landing on one's property be force of nature is not direct: Gregory v. Piper 1829
bb) Non-feasance does not amount to trespass: The Six Carpenters' Case 1610 - they entered a tavern and did not pay; rule developed: if you commit a tort (being there lawfully) you are a trespasser from the moment of your entering the premises.
b) Defenses and justification
aa) Leaving the gate open gives anyone with a legitimate reason to enter a permission to do so; he must be given reasonable notice to leave: Robson v. Hallet 1967
Allowing people frequently to use one's land will amount to consent: Lowery v. Walker 1911 - a man attacked by the owner's horse.
bb) Contractual license as justification: Hurst v. Picture Theatres 1915 - a man thought not to have paid was ordered out of the cinema although he had perfect reason to be there.
cc) Entering land in pursuance to police investigations: If there are reasonable beliefs in a cause of such action, this will justify the entering: Chic Fashions v. Jones 1968.
dd) Duress is no defence (you have a choice): Gibert v. Stone 1647.
ee) Necessity (yes, no, no):
Southport Corporation v. Esso Petroleum Co. Ltd. 1956 - ship 'landing' on land, releasing oil.
Rigby v. Chief Constable of Northhamptonshire 1985 - police setting psycho's house on fire.
Southwark London Borough Council v. Williams 1971 - homeless couple.
c) Miscellaneous
aa) Airspace: One has reasonable rights in one's airspace: Anchor Brewhouse v. Berkley House 1987. But an airplane flying over one's land is no harm: Bernstein v. Skyviews 1977 - no rights from heaven to the middle of the earth.
Errecting a sign above land is trespass to airspace: Kelson v. Imperial Tobacco 1957
bb) If the act is committed not on the plaintiff's land, but adjacent to it, an action lies if the act is not within the purpose of the adjacent land (i.e. a highway). Making noise is enough: Harrison v. Duke of Rutland 1893 - a man scaring away bird the duke wanted to hunt.
cc) Third parties' responsibility: League Against Cruel Sports v. Scott 1985 - protection promised; the injury could have reasonably been foreseen.
dd) Unlikely chain of causation: Scott v. Shephard 1773 - a squib thrown onto a market area was 'passed on', eventually hitting somebody - this was held as direct injury (diss. op. Blackstone).

3. Trespass to goods: This is now regulated in the Torts (Interference with Goods) Act 1977 - see Wrongful Interference with goods.