When Trees Cause Damage: How Arborist Reports Support Legal and Insurance Cases

What Is a Level 3 Tree Risk Assessment?
The International Society of Arboriculture (ISA) defines three levels of risk assessment. Level 3 is the most advanced and is typically used after a structural failure has occurred, when there are signs of decay or instability, to assess risk in a legal or insurance context, or when a comprehensive, court-ready report is required. Level 3 assessments follow the ANSI A300 (Part 9) standards and ISA Best Management Practices (BMPs). The arborist conducts a ground-based inspection using tools such as a sounding mallet, and evaluates targets within 1.5x the tree’s height. Risk is quantified based on likelihood of failure, likelihood of impact, and the severity of consequences.

Case Study: Legal Report Following Tree Failure

In a 2025 case in northeast Ohio, a large Pin Oak (Quercus palustris) failed during a windstorm. The co-dominant stem broke off and caused substantial damage to a nearby residence. Highlights from the investigation include: 55 mph wind gusts were recorded, with prevailing winds aligning with the failure direction. The tree exhibited a co-dominant union with included bark, a structurally weak configuration. A sounding mallet detected hollow resonance approximately 4 feet above ground, suggesting a vertical column of decay. The tree had not been pruned in over 11 years, well beyond the recommended 3–5 year inspection cycle for mature urban trees. A heavy population of carpenter ants was found at the wound site, indicating long-standing decay in the heartwood. Photographic evidence and onsite conditions were documented, and the risk to multiple targets—including a garage, fence, and play areas—was evaluated. The remaining tree structure was determined to be high risk, and removal was recommended as the only mitigation strategy that would reduce residual risk to an acceptable level.

Why Legal and Insurance Professionals Turn to Arborists
Tree risk assessments conducted by ISA Board Certified Master Arborists serve multiple purposes in legal and insurance contexts: clarify structural failure causes using standardized criteria, assess risk retroactively even after a tree or limb has fallen, document high-value targets within the fall zone, and deliver professional, defensible reports suitable for court or claims files. The report in this case provided critical information for the attorney representing the insurer and has since led to additional consultation requests for similar claims.

When to Involve an Expert
Attorneys, adjusters, and property managers may benefit from a Level 3 Tree Risk Assessment when tree failure results in injury, structural damage, or financial loss, a third-party expert is needed to determine preventability, or liability is in question and accurate documentation is essential. Reports can also help establish whether proper maintenance was followed and if mitigation strategies—such as cabling or structural pruning—were viable prior to failure.

Consulting Services Available
Trees and Gardens Consulting, LLC provides expert witness consulting, forensic tree failure investigations, and tree risk reports tailored to legal and insurance needs. Services are available throughout northeast Ohio and surrounding regions. To request a consultation, visit treesandgardensohio.com or contact Tina Graver directly through the contact page.