“How did the Galaxy Tab escape design patent infringement? This was the only device to be preliminarily enjoined (on appeal no less), and yet it was the one of the few devices to be spared the sledgehammer.”

Some initial reports used the fact that the jury let the Tab off the hook — despite the fact that its design seemed a clear imitation of the iPad’s — as proof that the verdict was not a rubber-stamp victory for Apple (AAPL).

Groklaw’s Pamela Jones, by contrast, took it as evidence that the entire verdict was “a farce” and won’t hold up under scrutiny.

Apple, for its part, is expected to appeal that element of the verdict — one of the few that didn’t go its way — and at least one expert thinks there’s a good chance it may prevail.

The mechanism by which that would happen is called Rule 50. It allows a judge to issue a directed verdict when the evidence permits only one reasonable conclusion — a conclusion different from the one the jury reached.

Directed verdicts are relatively uncommon, says Christopher Carani, a design law expert at McAndrews Held & Malloy. But in this case, he says, “Apple’s argument may have some traction and Judge [Lucy] Koh may well exercise this super-charged trump card in Apple’s favor.”

Like Professor Risch, he notes that Judge Koh had already granted a preliminary injunction against the Galaxy Tab 10.1 — a ruling that required a higher burden of proof than the questions of infringement and dilution the jury was asked to decide.

“Samsung appears to have created a [tablet] design that is likely to deceive an ordinary observer,” she wrote, citing one of the criteria for dilution, “inducing him to purchase one supposing it to be the other.”

Moreover, adds Carani, the language Judge Koh used in describing the Samsung tablet — “virtually indistinguishable,” ‘‘looks almost identical” and “looks virtually identical” — is even stronger than the “substantially the same” standard the jury was asked to apply.

Given all this, how could the jury conclude that the Galaxy Tab 10.1 did not rip off the iPad’s look and feel? Or, in legal terms, violate Apple’s “unregistered trade dress.”

The answer seems be that some jurors were confused about what it means for trade dress to be “unregistered.”

According to the federal code governing trademarks (15 USC § 1125), language echoed in the judge’s instructions, it’s illegal to copy the design of a product if it’s sufficiently famous — as famous, say, as the iPad. The design of such a product doesn’t actually have to be registered with the patent office to be protected from infringement or dilution.

It seems that the jury didn’t quite get that. Here’s what juror Manuel Ilagan told CNET‘s Greg Sandoval in a post-verdict interview:

“We were debating the unregistered trade dress claims. That took a while because some of the guys wanted to give [Apple] protection to round corners, the icons, and rectangles, but they were not registered. So, some of the jurors said ‘Why are we playing patent office? We’re not the patent office. It’s not even registered.’ And some of the jurors, when you look at the combination of those features, said it looks like an Apple. But we didn’t want to shut out Samsung from the market because we thought ‘OK, well, if Apple had tried to get a patent for all that stuff and didn’t, now they wanted us to be the ones to get it for them. We didn’t want to do that.”

Oops.

“Keep an eye on Apple’s Rule 50 motion for a directed verdict on the jury’s finding of non-infringement on the tablet design patent,” says design law expert Carani. “She just might grant it.”