Apple's Apple Watch patent bill just got bigger.
On Monday, October 5, U.S. District Judge James V. Selna ordered Apple to pay Masimo another $184 million in prejudgment interest on the $634 million a jury awarded the company last November. That takes Apple's total obligation in the case to roughly $818 million, and it does not include post-judgment interest that keeps accruing until the judgment is actually paid.
The ruling landed the same week Apple is pushing the Apple Watch Series 12 and Ultra 4 into the holiday shopping season. The money is a rounding error next to Apple's balance sheet, but it is a clean legal loss on the exact feature set Apple has spent three years arguing about in court.
Apple Tried the Windfall Argument and Lost
Apple's position was simple: adding interest on top of a nine-figure verdict would hand Masimo a windfall. Judge Selna disagreed.
He leaned on U.S. Supreme Court guidance that prejudgment interest "merely serves to make the patent owner whole." In plain terms, Masimo spent years being denied royalty payments it would have collected during the period Apple was infringing, and the interest is meant to backfill that gap rather than punish Apple.
Masimo wanted more. It asked the court to apply a 7 percent rate, which would have worked out to $243 million in interest, about $59 million above what it got. Selna declined and instead used Masimo's own borrowing rate, compounding annually from the start of the infringement.
So Apple caught a break on the rate, just not on the principle.
Where This Case Came From
This is not the blood oxygen fight most Apple Watch owners remember. It is a separate patent case with a lot of shared history.
- November 2025: A federal jury in California found that Apple Watch features, including heart-rate monitoring and notifications plus a workout mode, infringed a Masimo patent covering low-power pulse oximetry. Masimo was awarded $634 million, and the jury concluded all four asserted claims were infringed. It also agreed that certain Apple Watch models qualified as "patient monitors."
- July 2026: Apple lost its bid to overturn the verdict, and the court denied its request for a new trial.
- October 2026: Selna added the $184 million in prejudgment interest.
Reuters and TechCrunch covered the original $634 million verdict. Bloomberg Law and Law360 reported the new interest order, with MacRumors, AppleInsider and 9to5Mac following.
The patent at the center of this verdict expired in June 2022. That matters for anyone worried about their current watch. This judgment covers historical sales, and the ruling has no effect on the heart-rate features on current Apple Watch models.
The Other Masimo Case Is the One You Feel
Masimo is also behind the dispute that actually changed the product. That battle went through the U.S. International Trade Commission and produced an import ban on certain Apple Watch models, which forced Apple to disable the blood oxygen sensor on newly sold watches in the U.S. in early 2024.
Apple later reworked the feature and brought it back, and blood oxygen data returned to the Vitals screen in a recent iOS update. If you own a Series 9 or Ultra 2 from that window, you have felt the practical effect of this fight far more than any courtroom dollar figure.
That is what makes this week's ruling interesting to watch. Apple is appealing, and so far the courts keep siding with the smaller company on the substance. Read the interest order alongside our look at the $5.7 billion Taptic Engine verdict and the AliveCor import ban outcome and a pattern shows up: Apple's health sensors keep dragging it into courtrooms, and the company keeps losing the ones that reach a verdict.
What It Means for Apple Watch Buyers
Nothing changes about the watch on your wrist today, and nothing changes about the watch you can buy this week.
A few things worth knowing anyway:
- No feature removal is coming from this ruling. The patent expired in 2022, so there is nothing left to design around.
- Apple is appealing, so the number could still move. The $818 million total is what Apple owes under the current judgment, not necessarily the final figure.
- The blood oxygen feature is the real-world lever. If Apple ever loses the broader fight in a way that forces another change, that is the thing owners would notice.
The practical shopping picture has not moved either. The Apple Watch Series 12 is the current mainstream pick, the Apple Watch Ultra 4 is the one for people who want the biggest screen and battery, and Prime Big Deal Days discounts are the likeliest place to save on either right now. If you are weighing the two, our Series 12 and Ultra 4 breakdown covers the differences that actually matter.
Bottom Line
Apple now owes Masimo about $818 million, plus interest that keeps running until it pays. The judge rejected Apple's windfall argument, knocked down Masimo's 7 percent ask, and left both sides with something to appeal.
For Apple Watch owners, the headline is boring in the best way. The patent expired four years ago, no current feature is affected, and the only place this fight ever touched a real product was the blood oxygen sensor. That is the case to keep watching, not the interest line.
Sources: Bloomberg Law; Law360; Reuters and TechCrunch (November 2025 verdict); MacRumors; AppleInsider; 9to5Mac. The October 5 interest order is reported by Bloomberg Law and Law360; figures are attributed to those reports. Apple has not commented publicly on the interest ruling, and the case remains under appeal.
