Apple owes Masimo about $818M after a judge adds $184M in interest to the Watch patent verdict

Somebody's Apple Watch will flag a high heart rate tonight, and the alert will look the same as it did last week. The Masimo patent in this case covered a way to measure blood oxygen using little power ^[9]. It expired in June 2022, so the ruling concerns historical Watch sales and has no effect on heart-rate features in current models ^[15].

The people who need to read this order are the finance and legal staff at companies that ship health sensors. The jury set its $634 million award in November 2025 ^[3], and the damages were the license fees Apple should have paid ^[8]. A company that contests a royalty claim keeps that money while the case runs. Selna's order charges for that time. The court used Masimo's own borrowing rate, compounded annually from when the infringement began ^[7]. According to Bloomberg Law's report, the interest came to $184 million ^[1]. That adds about 29% to the original award ^[16].

Apple argued the interest would be a windfall for Masimo. Selna rejected that ^[4], citing Supreme Court guidance that "interest from the time that the royalty payments would have been received merely serves to make the patent owner whole" ^[5]. Masimo's 7% request would have put the interest at about 38% of the award ^[17]. The lower rate saved Apple $59 million ^[18]. In nominal dollars, contesting cost Apple more than licensing would have. The extra is what a late royalty costs at the claimant's borrowing rate, and the judge declined to set it higher ^[6].

The import fight is the one that reached buyers. Apple disabled blood oxygen on affected newly sold models after the ban ^[10]. It introduced a redesigned version of the feature in 2025 ^[11].

For a team weighing a sensor patent claim, the forcing question is whether the claimant's remedy can reach the product. In this case it could not, because the patent had expired ^[15]. Losing that kind of case costs the royalty plus the claimant's compounded borrowing cost ^[7], plus post-judgment interest until payment ^[13]. I'd treat that branch as a financing decision and weigh it against the litigation budget. The import case went the other way: the remedy reached the product, and people bought watches with a feature switched off ^[10]. In that branch I'd license or redesign early. The tradeoff is paying for claims a court might have thrown out. Apple tried to overturn or reduce this award, and Selna upheld the verdict in July ^[14].