Concurrent causation is a problem familiar to delay experts but it is equally important in the quantification of loss and expense and damages. The basic question is the same: where two or more events have contributed to the same loss, and one or more of those events is the responsibility of the claimant rather than the respondent, how should the loss be assessed? The answer is not always the same as for delay, and quantum experts must understand the distinction.
On the time side, the predominant approach in jurisdictions following the English law tradition is that the contractor is entitled to a full extension of time for the period of concurrent delay (the 'time' element of the Malmaison principle), but is not entitled to recover prolongation cost for that period unless it can prove that the employer's event was the dominant cause of the additional cost (the 'no money' element). This 'time but no money' approach was confirmed by the English courts in Walter Lilly v Mackay and is widely applied in international arbitration.
The rationale for the 'no money' element is that the contractor has not in fact suffered any additional cost as a result of the employer's event during the period of concurrent delay, because the contractor's own delay would have caused the same cost in any event. The contractor is in the position it would have been in but for the employer's event, and damages are intended to put the claimant in that position. To award the contractor prolongation cost for the period of concurrent delay would over-compensate the contractor and impose on the employer a cost that the employer's event did not in fact cause.
Concurrent causation can also arise in relation to discrete heads of cost rather than periods of delay. For example, the contractor may have incurred additional cost in remedying defective works for which the employer is partly responsible (because of a design defect) and partly responsible itself (because of poor workmanship). The proper apportionment of the cost between the two causes is a matter for the quantum expert, and may involve a detailed analysis of the contribution of each cause to the additional cost incurred.
The methodology for apportionment varies with the nature of the cost. Where the cost is divisible — for example, where part of the remedial work is attributable to the design defect and part to the poor workmanship — the apportionment may be relatively straightforward. Where the cost is indivisible — for example, where the remedial work would have been the same regardless of which of the two causes had operated alone — the apportionment is more difficult, and may require recourse to legal principles on the apportionment of indivisible loss.
Concurrent causation also raises issues of mitigation. The claimant has a duty to take reasonable steps to mitigate its loss, and that duty applies regardless of who is responsible for the original event. Where the claimant could have taken reasonable steps to avoid or reduce the loss but failed to do so, the loss may be reduced or disallowed even if the original event was the respondent's responsibility.
Our quantum experts at Construction Expert Witness routinely address concurrent causation issues on disputes across the GCC. We work closely with the parties' legal teams to ensure that the quantum analysis properly reflects the legal principles applicable to concurrent causation in the relevant jurisdiction, and we present the analysis with the transparency that tribunals require.