Can I be sued twice over the same thing?

15 Jul 2026

Litigation is expensive and stressful and typically lasts years. For that reason, there are strong public policy considerations around finality surrounding litigation.

Estoppel per rem judicatam is the legal principle which says that where a dispute has already been determined, it cannot be raised again. Cause of action estoppel is part of this, and relates to an issue which has already been argued and decided.

The same public policy – that is, that there should be finality in litigation and that a party should not be vexed twice in the same matter – leads to a further principle called abuse of process.

Abuse of process goes further than res judicata by disallowing a litigant to bring a claim which could or should have been brought at the same time as previous litigation. This rule is also known as “the rule in Henderson v Henderson”, an English case which set out that:

Where a given matter becomes the subject of litigation in, and of adjudication by, a Court of competent jurisdiction, the Court requires part parties to that litigation to bring forward their whole case, and will not (except under special circumstances) permit the same parties to open the same subject of litigation in respect of matter which might have been brought forward as part of the subject in contest, but which was not brought forward, only because they have, from negligence, inadvertence, or even accident, omitted part of their case.

We recently applied for and obtained summary judgment, striking out proceedings on the basis of Henderson v Henderson abuse of process, in Keys v Patterson [2026] NZHC 1879.

The defendant, Ms Patterson, had previously been the defendant in proceeding Keys v Patterson & Ors [2025] NZHC 2676 (Prior Proceeding).

The Prior Proceeding was a claim against Ms Patterson following the sale of her property to the Plaintiffs. It included a claim against Ms Patterson for a breach of vendor warranties in the agreement for sale and purchase (ASP).

Clause 6.2(5) of the ASP sets our vendor warranties in respect of works done to the property. Subclause (a) contains a warranty that where the vendor did, caused or permitted to be done any work, any permits, resource consents or building consents required by law were obtained.   Clause 6.2(5)(b) of the ASP is a warranty that any works completed were completed in compliance with permits or consents obtained.

The claim in the Prior Proceeding was for a breach of clause 6.2(5)(b) of the ASP but did not include a claim for a breach of clause 6.2(a) of the ASP. Nine months before the trial, the purchasers’ expert advised the purchasers and their lawyers that he considered that there may be a claim in respect of clause 6.2(a) of the ASP as well. The purchasers updated their claim some four months later, but did not include a claim for a breach of clause 6.2(a) of the ASP.

During the trial, the purchasers attempted to amend their claim to include a claim for clause 6.2(a) of the ASP. Given this had not been claimed previously, Ms Patterson had not taken any steps to address that claim. She opposed the application to amend the claim. The judge in the Prior Proceeding agreed that bringing the claim at this late stage would cause her prejudice and disallowed the claim to be brought.

The purchasers were unsuccessful in the Prior Proceeding. The purchasers appealed the judgment. The appeal is pending. In addition to that, the purchasers brought new proceedings, in respect of only clause 6.2(a) of the ASP.

Ms Patterson applied for the new proceeding to be struck off, on the basis that they had knowledge of the potential for the claim well before the close of pleadings date and could and should have brought that claim in the Prior Proceeding if they so wished to do so. She said that bringing the claim now, would be an abuse of process.

The High Court held that the clause 6.2(5)(a) claim could and should have been brought in the first proceedings and that there was no good reason for it to have been brought in a second proceeding. The judge held that one proceeding would have done and that raising this claim now would be unfair and oppressive to Ms Patterson. As a result, the claim was struck off.

The reasons for arriving at this decision included that there was significant overlap between the claims which arise out of the same complex background facts and the same contract. The judge noted that the roof membrane work had already been traversed in detail in the Prior Proceeding. This new proceeding would require Ms Patterson to litigate the same subject matter, having already faced 14 days of trial in the Prior Proceeding.

He further noted that a second proceeding would unlikely to be heard for some years, would involve a four or five day trial and incur significant cost. The appeal also complicated bringing a second proceeding as some facts may be reconsidered there and impact this proceeding.

This decision was significant for Ms Patterson, who would otherwise have had to traverse the same subject matter over many more years of litigation, having just come out of four years of litigation and a three week trial.

If you are uncertain about whether a claim brought against you has already been determined or ought to have been brought, get in touch with our Dispute Resolution team.