A federal court jury is having a difficult time reaching a verdict in a complex copyright infringement trial pitting Oracle against Google.

A question posed late Thursday in a note from one of the 12 jurors raised the specter of an impasse after lawyers on both sides spent two weeks trying to make their cases. The evidence included testimony from Oracle CEO Larry Ellison and Google CEO Larry Page.

Thursday’s note asked U.S. District Judge William Alsup what would happen if jurors couldn’t agree on a verdict. The note also indicated some jurors weren’t budging from their positions.

The question came after more than 20 hours of jury deliberations spread over four days.

Alsup called the jury into the San Francisco courtroom to give them a pep talk before sending them home for the day.

The jury is debating Oracle’s allegations that Google built its popular Android software for mobile devices by stealing some of the technology from Java, a programming platform that Oracle bought two years ago.

Oracle is hoping to win hundreds of millions of dollars in damages and a court order that would require Google to get a licensing agreement to keep using elements of Java in Android.

Google says it only used parts of Java that have always been freely available. The company also argues its actions fall under the “fair use” provision of U.S. copyright law.

If the jury can’t reach a unanimous verdict on the copyright infringement allegations, Alsup told them that they will move on to a second phase of a trial to determine if Android violates two Java patents. If the copyright case ends in a deadlocked jury, Alsup said it probably will be re-tried in the future.