Because the allegations are for a period when the patent was not expired.

Getting qualified people to dig up prior art and write responses ain't cheap.

The patent is expired now, but they can still sue for infringement that occurred during the life of the patent. In fact, this is how it goes for many patents given the lifecycle.

Because you don't just automatically win because the patent is expired. You have to hire a lawyer to research the patent and find out it's expired, then, at minimum, your lawyer has to go to court and prove that the patent is expired.

But patent terms are 20 years. It had clearly been more than 20 years.

Why didn’t the lawyer simply state this in their counterclaim? I don’t actually see it anywhere in the counterclaim.

You can, in some cases, sue for damages accrued up to six years in the past. You don't have to sue for those before the patent expires. You just stop accruing new damages when the patent expires. Past damages is what was allegedly at issue here. (Which is why the attorneys were talking about "marking," as it's a factor in whether you can get pre-suit damages for some types of claims in some cases.)

Thank you for this!

>You have to hire a lawyer to research the patent and find out it's expired

You can do this yourself though