The law regarding trees and liability is generally well known and refreshingly simple; the owner of the tree is responsible for the tree and for maintaining it. Any damage caused by a tree is, therefore, the owner's responsibility. However, what is perhaps less well known is the degree of maintenance and upkeep required of a tree owner and the various liabilities he is exposed to.

The case of Thompson-Schab v Costaki [1956] 1 WLR 335established that roots and branches of a tree can cause private nuisance to a neighbouring landowner if they cause physical damage to the neighbour's land, buildings or vegetation or if they interfere unreasonably with the neighbouring owner's enjoyment of his land.

Case law affirms that a tree owner has a duty to do that which is reasonable in all the circumstances to minimise or prevent any risk of interference with or damage to any neighbouring property where the tree owner knew, or ought to have known, that tree roots or branches were encroaching onto neighbouring land. It must also have been reasonably foreseeable that there was a risk of damage to the neighbouring property, or to the enjoyment of the neighbouring property, as a result of the encroachment.

An individual landowner, with trees on his property, should therefore regularly and informally assess the health and state of his trees. A regular and informal assessment should be sufficient to mitigate the tree owner's civil liability. This has been confirmed by the recent High Court case of Stagecoach South Western Trains Limited v Hind & Steel (2014).

However, a tree owner should not be too quick to rest easy. If the tree owner is not knowledgeable about trees, or if an informal assessment reveals any issues, then there is an expectation that the tree owner will instruct a tree expert in the matter.

Most importantly, tree owners need to note that, when it comes to liability, there will be different tests imposed by regulators, depending on the liability being assessed. Should a falling branch or tree result in injury or a fatality then there will not only be civil liability to contend with, but also criminal. The tree owner could also face charges of gross negligence manslaughter, as well as charges brought under health and safety legislation in the case of serious injury. Health and safety legislation imposes a test of reasonable practicability, i.e. the tree owner would need to prove that it was not reasonably practicable for him to have done more than he did. In practice, this is an extremely difficult test to prove. With large estates, the owner of the property is often a company and, in such a situation, a fatality could lead to charges being pressed under the Corporate Manslaughter Act.

Tree owners clearly need to be both wary and aware, especially if their trees overhang neighbouring property or areas accessible by members of the public. It is vital that tree owners carry out regular inspections and act promptly if they have any concerns, and it is strongly advised that all such inspections are documented. For, although the tree owner may be able to prove that he should not be liable to pay compensation in cases of injury or death, he may still face criminal prosecution. In such a scenario, it is vital to have hard evidence that all appropriate measures were taken.