Dayco Europe SRL v Gates Unitta Asia Company & Ors

The court must restrict expert evidence to that which is reasonably required to resolve the proceedings. Where a patent concerns technology spanning distinct specialist fields, the skilled team may properly include expertise in each field. Permission to call separate experts is appropriate where their evidence addresses genuinely different areas and can be controlled to avoid duplication, unnecessary length and procedural unfairness.

The claimant sought permission to call two experts in patent proceedings concerning a toothed power-transmission belt designed for use in high-temperature engine rooms. One expert had mechanical-engineering expertise and the other textile expertise. The defendants opposed the application, relying on the availability of an expert with expertise in both fields and concerns about trial length and a level playing field. The issue was whether the interests of justice required permission for both experts.

1. Expert evidence. The court has a duty to restrict expert evidence to that which is reasonably required to resolve the proceedings.
2. Relevant expertise. The patent was directed to a skilled team whose expertise necessarily included both mechanical engineering and textile technology. The claimant’s proposed experts each had expertise in one of those fields but none in the other.
3. Balancing considerations. The defendants’ concerns about trial length, duplication and procedural equality were serious. However, the court considered that separate experts were unlikely unduly to lengthen the trial because each could not answer questions outside the other’s field. The experts were expected to avoid duplication and keep their reports no longer than necessary. The trial judge could also manage the evidence so as to minimise any perception of an unequal playing field.
4. Order. In the circumstances, the interests of justice required the application to be allowed. Permission was granted for the claimant to call both experts.

Not stated in the judgment; this was a first-instance procedural application in the Patents Court.