Your expert's 200-page report won't be read. Both experts will argue in real time.

When the court brings your experts into the same room

You've spent a significant amount on a patent infringement suit. Your expert has a 200-page report. Their expert has a 200-page report. The judge reads neither. Instead, both experts sit at the same table, the judge asks them questions together, and they argue it out in real time. That's hot tubbing. And the Delhi High Court can order it whether you want it or not.

The stakes are immediate: if you're in a commercial suit with technical evidence, the court can bypass the entire traditional examination-in-chief and cross-examination cycle. Your carefully prepared expert testimony gets compressed into a single session. The question is: who decides this happens, and how does the court tailor the process to your case?

Two ways the court can pull the trigger

The Delhi High Court (Original Side) Rules, 2018 give the court two distinct mechanisms to permit expert testimony using the hot tubbing technique. Neither requires your consent.

First: the court acts on its own motion. The judge sees a case with conflicting technical reports—say, a software copyright dispute where both sides have engineers claiming opposite things about source code. The court can simply decide, without any application from either party, that the experts will testify together. This is the sua sponte power. It's the court's case management authority in action. You don't get a veto.

Second: a party applies for it. You file an application asking the court to permit expert testimony and specifically to use the hot tubbing technique. This is the adversarial initiation mechanism. You frame the need: the evidence is too technical, the reports are too voluminous, the traditional method will take weeks. You ask the court to bring the experts together.

Once the court permits the expert to testify—by either route—it passes orders covering the manner of recordal, the documents the expert will rely on, and the fee payable to the expert. The hot tubbing protocol itself is illustrative, set out in Annexure G to the Rules. But here's the critical point: the court is not bound by that protocol.

How the protocol gets customised to your case

The Rules explicitly state that the standard protocol for hot tubbing must be "appropriately moulded" by the court. This isn't a one-size-fits-all procedure. The court customises it based on two criteria:

1. The facts of the case. A pharmaceutical patent case involving chemical equivalence is factually different from a construction contract dispute about structural defects. The facts determine how the experts should interact—whether they should present their opinions side-by-side, whether they should respond to each other's conclusions in writing first, or whether the judge should lead the questioning.

2. The circumstances of each case. This is broader. It includes the stage of the litigation, the volume of evidence, the number of experts, the urgency of the matter, and even the availability of the experts. A case where one expert is based in Singapore and the other in Mumbai will have different logistical circumstances than one where both are local.

What this means for you: when you file an application for hot tubbing, you must argue not just that the technique should be used, but how it should be modified for your specific dispute. The court's subsequent order will dictate the specifics—the recordal method, the documents to be used, the payment structure for the expert. If you don't address the customisation criteria in your application, you leave the court to guess what works for your case.

Three questions every commercial litigator should ask

If you're handling a case where expert testimony matters—and in commercial litigation, that's most cases—here are the moves to make:

1. File early for hot tubbing if your case has conflicting technical evidence. Don't wait for the court to do it sua sponte. If you file first, you control the narrative. Your application frames why the technique is necessary and how the protocol should be customised. The other side will have to respond to your framing.

2. Address the customisation criteria explicitly in your application. Don't just say "the court may use hot tubbing." Say: "Given that the dispute concerns the interpretation of three specific clauses in a software licensing agreement, and both experts have submitted reports running over 150 pages each, the court should modify the standard protocol to require the experts to submit a joint statement of agreed and disputed facts before the hot tubbing session." That's specific. That's useful. That's what the court needs.

3. Prepare your expert for the hot tubbing session differently than for traditional testimony. In a hot tubbing session, your expert doesn't just answer questions from your counsel. They respond to the judge's questions, to the other expert's statements, and sometimes to the other side's counsel—all in the same session. The expert needs to be comfortable with confrontation, with real-time rebuttal, and with explaining technical concepts to a judge who may not have a technical background. This is a different skill set from writing a report.

What this means for your next case

The hot tubbing mechanism under the Delhi High Court Rules is a powerful case management tool. It compresses weeks of expert testimony into a single session. It forces experts to engage with each other directly, rather than through the filter of cross-examination. And it gives the judge the ability to ask questions in real time, clarifying technical points as they arise.

But it's not automatic. The court must decide to use it—either on its own motion or on your application. And once decided, the protocol must be customised to the facts and circumstances of your case. If you don't address the customisation criteria, you risk getting a generic procedure that doesn't fit your dispute.

THE PLAY: In any commercial suit with conflicting expert evidence, file an application for hot tubbing before the first case management hearing, and include a proposed customised protocol that addresses the specific facts and circumstances of your dispute.

If you're in this spot: the court can order hot tubbing whether you ask for it or not. But if you ask for it first, and you show the court exactly how the protocol should be moulded to your case, you control the process. That's the difference between being reactive and being strategic.