A jury has found that Google infringed Oracle's Java copyrights in Android but could not decide unanimously if the infringement was protected by "fair use."

The jury's verdict, delivered Monday after a week of deliberation, is a partial victory for Oracle in its lawsuit against Google, but Oracle will have to wait longer -- possibly for a retrial -- to see whether Google will escape liability with its claim of fair use.

Google's attorney, Robert Van Nest, immediately told the judge that Google would file for a mistrial. Google's argument will be that the same jury must decide both the copyright infringement and fair use issues. The judge told both sides to submit legal briefs on that issue.

After the verdict was delivered Monday, the trial moved immediately into the patents phase of the case, with Oracle making its opening statement. The trial is in three parts, to address copyrights, patents, and any damages Oracle should receive.

But although the patents phase is under way, the copyright phase is far from concluded. As well as the outstanding issue of fair use, Judge William Alsup, who is hearing the case, must decide whether Oracle's Java APIs (application programming interfaces) can be copyrighted at all under U.S. law.

Historically, APIs have not been considered copyrightable. But Oracle argues that the the "structure, sequence and organization" of the 166 API packages in Java are sufficiently complex to merit protection.

Google has until late Monday to submit its arguments on that issue to Alsup. The judge has not said when he will rule on the law question, but some observers expect it to happen before the damages phase of the trial begins in about two weeks.

"We appreciate the jury's efforts and know that fair use and infringement are two sides of the same coin," Google said in a statement sent via email. "The core issue is whether the APIs here are copyrightable, and that's for the court to decide. We expect to prevail on this issue and Oracle's other claims."

Oracle thanked the jury for the verdict. "The overwhelming evidence demonstrated that Google knew it needed a license and that its unauthorized fork of Java in Android shattered Java's central write once run anywhere principle," it said.

At least one industry analyst was troubled by the jury's decision. "I was a bit disappointed by the verdict, as I think that the precedent of copyright for APIs opens up a real can of worms and potentially stifles software innovation," Forrester analyst Jeffrey Hammond said via email.

"The silver lining was the deadlock on fair use," he said.

The jury actually had several copyright questions to decide on the verdict form, although the ones about the API infringement and fair use were considered the most significant.

On another point, the jury decided Sun's public statements about Java were sufficient to to convince Google that it didn't need a license to use Java. But in another setback for Google, the jury decided there was insufficient evidence to show Google relied on those statements. That means the jury wasn't swayed by a much-discussed blog post from then-Sun CEO Jonathan Schwartz, in which he congratulated Google on its release of Android and said that it would be good for Java.

Google did prevail on some other issues, including whether it infringed a copyright for Oracle's Java API documentation. The jury also ruled in Google's favor in two out of three instances where it was accused of copying a small amount of code line-by-line from Java.

It's not clear yet when the fair use issue will be put to a jury again, and Alsup has a few of options at his disposal. Last week he said he might resubmit the question to the jury after the patents phase, but the lawyers for Oracle and Google were both opposed to that idea and favor a new trial.

Fair use allows the copying of creative works for certain limited purposes, such as teaching, commentary and satire. The jury in this case considered factors such as whether Android was "transformative," meaning did it amount to a new creation or was it simply derivative from the Java APIs. They also considered how much of the work as a whole was copied; whether the use was commercial; and how much harm Oracle suffered as a result.

The patents phase of the trial that just started is expected to last about two weeks. Google will make its opening statement Tuesday morning and then Oracle will call its first witness to the stand.

James Niccolai covers data centers and general technology news for IDG News Service. Follow James on Twitter at @jniccolai. James's e-mail address is james_niccolai@idg.com