Expert Evidence in Access Consulting and Architectural Disputes: Lessons from Makita v Sprowles

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Tuesday, 12 May 2026 14:36

Tuesday, 12 May 2026 14:07

Gary J Finn

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Expert Evidence in Access Consulting and Architectural Disputes: Lessons from Makita v Sprowles

Key facts of the case (taken straight from the judgment):

• The plaintiff, Ms Sprowles, was an employee of Makita (Australia) Pty Ltd.
• On 30 June 1986 she fell while descending internal concrete stairs at her workplace. The stairs ran from the rooftop car park down to the office level where she worked.
• She gave evidence that her foot simply “went out from underneath her”.
• She alleged the fall was caused by the slippery condition of the stair treads (very smooth concrete without a non-slip finish).
• At first instance she called Associate Professor Morton, a physicist who specialised in the investigation of slipping accidents.
• Morton inspected the stairs (some nine years after the accident), tested the tread surfaces with various shoe materials, and also tested the plaintiff’s actual shoe.
• His conclusions (set out in the judgment at the trial reasons) included: “The tread surfaces are very smooth and are not provided with a non-slip finish throughout as is required by Ordinance 70”; in clean, dry condition the treads were adequately slip-resistant only for footwear of inherently high-grip materials; the interface between the plaintiff’s shoe and the tread should not be classed as “very slippery” but the level of grip was “below that needed for a reliable margin of safety”; and the accident was caused by the inadequate frictional grip afforded by the smooth concrete stair treads.
• The trial judge accepted that evidence, found Makita negligent, and awarded damages.
• (We stop there because my instructions are to prepare an expert report without knowledge that the Court of Appeal ultimately allowed the appeal and held the expert evidence inadmissible or of no weight.)

It is worth noting that the expert conducted tests on the stairs years after the accident, and in that time, conditions may well have changed. This article does not seek to vindicate the Plaintiff in the real matter, but is merely an exercise to expose the reasoning for the weight given by the Court of Appeal to the expert witness report. 

At Sydney Access Consultants, we prepare detailed reports for clients, councils, certifiers and tribunals on Specialist Disability Accommodation (SDA) compliance, access audits, and building design issues. When those reports are used in NCAT, the court or other dispute resolution forums, they must meet the highest standards of independence and transparency.

A landmark decision that continues to set the benchmark for expert evidence in New South Wales is Makita (Australia) Pty Ltd v Sprowles [2001] NSWCA 305. In that case, the NSW Court of Appeal, per Heydon JA at paragraph [85], set out the essential requirements for an expert report to be admissible and given proper weight. The Court made it clear that an expert must:

• clearly identify the specialised field of knowledge on which the opinion is based;
• set out the facts and assumptions relied upon;
• describe the methodology used;
• explain step by step how that specialised knowledge is applied to the facts to reach each conclusion; and
• ensure the opinion is wholly or substantially based on the expert’s own expertise rather than lay inference, advocacy or unstated assumptions.

These principles protect everyone involved in a dispute: the Tribunal or court receives reliable, testable evidence, and the parties know exactly why the expert has reached a particular view.

To show how these requirements work in practice, we have prepared the following model expert witness report. It is written as though Gary John Finn had been retained to give evidence on a hypothetical slip-resistance issue (a common question in architectural design and access compliance). The report follows the Makita criteria to the letter and demonstrates the transparent, structured approach we take at Sydney Access Consultants when preparing any formal opinion for disability access consultant work, SDA assessments or NCC compliance matters.

MODEL EXPERT WITNESS REPORT

Prepared by Gary John Finn, Architect and Access Consultant

Matter:

Hypothetical Slip-Resistance Assessment (illustrating Makita principles)

Date of report: 12 May 2026

1. Qualifications and field of specialised knowledge

I am Gary John Finn, Registered Architect (NSW Registration No. 5774) and holder of the Certificate IV in Access Consulting. I have more than 30 years’ experience in architectural practice, access auditing and Specialist Disability Accommodation (SDA) assessments under the NDIS framework. I am an Accredited SDA Assessor, a member of the Association of Consultants in Access Australia (ACAA) and regularly provide expert compliance opinions on pedestrian surfaces, slip resistance, and Disability Discrimination Act / National Construction Code (NCC) access requirements. My specialised knowledge lies in the practical application of Australian Standards (including AS 4586 and AS 4663), the National Construction Code (NCC), and NDIS SDA Design Standards to real-world building projects.

2. Instructions

I was instructed to provide an independent expert opinion on whether the concrete stair treads at the premises were slippery and whether that condition contributed to a fall on 30 June 1986. I was asked to identify all facts and assumptions, describe my methodology fully, and explain step by step how my specialised knowledge leads to each conclusion.

3. Materials and facts relied upon Facts observed by me

• I inspected the stair treads on 15 March 2026 and took surface roughness measurements (Rz and Ra parameters) at 20 locations using a calibrated Mitutoyo Surftest SJ-210.
• I performed pendulum friction tests (British Pendulum Tester, calibrated per AS 4663) in dry and wet conditions using slider materials that replicate typical pedestrian footwear.

Facts assumed (and proved by other evidence)

• The person was descending the stairs in normal work footwear at a normal walking pace.
• The stairs were clean, dry concrete without any applied non-slip coating or treatment at the time of the incident.
• No foreign substances were present on the treads.

All assumed facts are identified in this report and are separately proved by lay evidence or documents.

4. Methodology

I applied established protocols under AS 4663:2013 (Slip resistance measurement of existing pedestrian surfaces) and AS 4586 (Slip resistance classification of new pedestrian surface materials). Testing was conducted at 20 °C and 50 % relative humidity. Raw data, calibration certificates and photographs are annexed.

5. Application of specialised knowledge to the facts and reasoning

Slip resistance is governed by the interaction of surface micro-texture, footwear material and pedestrian gait. Smooth concrete treads (measured Ra 4.8 µm) provide minimal mechanical interlocking with common soles, resulting in a low dynamic coefficient of friction. My pendulum tests returned an average Slip Resistance Value (SRV) of 22 in dry conditions, well below the recognised safe threshold of SRV 35–44 (P3 classification) required for internal stairs under AS 4586-2013 and the National Construction Code.

Step by step:

• The tread smoothness falls into the “very smooth” category, known to produce inadequate grip.
• The absence of any slip-resistant finish removes both macro- and micro-texture.
• Normal walking descent requires a coefficient of friction of approximately 0.3–0.4; the measured value was 0.22.
• The AS 1428.1 demands slip-resistant nosings with a minimum 30% luminance contrast located on each tread, but those were absent.
• Therefore, the treads did not provide a reliable margin of safety.

This reasoning is based entirely on my specialised knowledge of access standards and surface compliance testing.

6. Opinion

In my opinion, to a high degree of professional certainty:

(a) The concrete stair treads were very smooth and lacked the requisite slip-resistant finish, as well as lacking nosings at each tread to AS 1428.1.

(b) They provided an inadequate frictional grip for normal pedestrian footwear.

(c) The level of grip was below that needed for a reliable margin of safety.

(d) The inadequate grip was a significant contributing cause of the fall.

7. Limitations and independence

I have no prior involvement with any party. I have read and agree to be bound by the Expert Witness Code of Conduct. My sole duty is to assist the Tribunal or court impartially.

Appendices

A – Curriculum Vitae

B – Raw test data and calibration certificates

C – Photographs

D – Relevant standards and literature

Signed: Gary John Finn Registered Architect #5774 (NSW) Certificate IV in Access Consulting Accredited SDA Assessor

Why this matters for your project

Whether you are a client, builder, certifier or fellow architect, insisting on expert reports that meet the Makita standard protects everyone. At Sydney Access Consultants, every formal opinion we prepare follows this disciplined approach so that councils, NDIS auditors, tribunals and courts can rely on it with confidence.

This structured method is particularly valuable for disability access consultant reports, SDA compliance assessments, performance solutions and access audits across New South Wales. It ensures clear, defensible evidence in NCAT proceedings or court matters involving slip resistance, pedestrian surfaces or broader NCC access requirements.

Gary John Finn Architect #5774 (NSW) | Certified Access Consultant Sydney Access Consultants sydneyaccessconsultants.com.au