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Norman Waterhouse

Tree damaging activity criminal prosecution

The City of Unley’s recent prosecution of two adjoining land owners and an arborist in relation to alleged tree damaging activity is one of the most significant regulated tree decisions to come out of the ERD Court (decision here).


In 2015, two adjoining land owners jointly engaged an arborist to prune two regulated trees that were sited on a neighbouring property which shared common boundaries. According to the Council’s arborist, what was pruned was 95-99% of the crown of one of the trees and 45-65% of the other.

The Council proceeded to prosecute the adjoining owners and the arborist for undertaking tree damaging activity without development approval. It also charged the arborist with offences pursuant to Section 19 of the Development Act 1993 for failing to produce documents and answer questions of an authorised officer.

Prior to the hearing one of the adjoining owners pleaded guilty. The other adjoining owner and the arborist pleaded not guilty. After 9 days of evidence His Honour Judge Costello was ultimately not satisfied beyond reasonable doubt that what occurred to the trees was a tree damaging activity and acquitted them of that offence. The arborist was found guilty of the Section 19 offences.

There were several key findings.

Onus of proving tree-damaging activity

Regulation 6A(8) of the Development Regulations 2008 excludes pruning from the definition of tree damaging activity, in certain circumstances where it does not remove more than 30% of the crown of the tree.

Back in 2014, Judge Costello held in The City of Adelaide v BFR Pty Ltd [2014] SAERDC 37 that the defendants carried the onus of establishing whether they came within the exclusion. His Honour further held that this onus was established on the balance of probabilities, rather than the criminal standard, of beyond reasonable doubt.

However, upon this being challenged by the defendants in this prosecution, his Honour declined to follow his 2014 decision, as in his view, Regulation 6A(8) cuts down the scope of the definition of development by way of definition (rather than by way of exception), and therefore it fell for the prosecution to establish that the exclusion did not apply beyond reasonable doubt.

What constitutes the ‘crown’ of a tree?

The term ‘crown’ as it is used in Regulation 6A(8) is not defined in either the Act or Regulations.

Both arborists that gave evidence were of the view that the crown was defined as the total of all branches in the tree that have live foliage. The Council however argued that it extended further to include all branches.

His Honour held that the term ‘crown’ should be given the meaning used in common parlance, relying on the definition in the Macquarie dictionary of ‘the leaves and living braches of the tree’.

This had particular relevance to this matter as the case for the accused arborist was that the trees were infested with mistletoe, which being a parasite is such that it is not part of the leaves of the tree and therefore not to be included within the 30% calculation.

What does it mean to ‘cause’ tree damaging activity?

This question arose in the context of the adjoining owners engaging the arborist to undertake the pruning work on the trees. In particular, it was argued by the adjoining owner that he directed the work to be undertaken within the limits of the law and the fact that the arborist may have gone beyond that, was not something which he had caused.

Given the Court’s ultimate finding that what occurred was not tree-damaging activity, this was strictly not necessary to be determined, nonetheless His Honour held that in order to prove its case that the adjoining owner has ‘caused’ tree damaging activity, the Council would need to show that he:

  • had the authority to direct the arborist to undertake the work that was done on the trees;
  • knew that the work that was undertaken on the trees would be undertaken; and
  • intended that the work which was undertaken would be undertaken.

His Honour was ultimately not satisfied that this had been proved beyond reasonable doubt.


His Honour found both the adjoining owner (who pleaded not guilty) and the arborist not guilty of undertaking tree-damaging activity without approval.

Given the other adjoining owner had pleaded guilty, he was still sentenced as if he had undertaken tree-damaging activity and was fined $300 without conviction.

The arborist, in his personal capacity, was also fined $1,250 for each section 19 offence without a conviction being recorded.

This isn’t however the end of this matter, as the Council have appealed to the Supreme Court. The hearing of the appeal is yet to take place.

For more specific information on any of the material contained in this article please contact Aden Miegel on +61 8 8217 1342 or


5 February 2020



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