Google's head of Android and senior vice president, Andy Rubin, is the latest person from the company to be called back into the Oracle-Google patent trial.

Rubin was called as there is a focus on what he knew about the patents belonging to Sun Microsystems. According to CNET, Rubin evaded questions as he did during his last appearance.

Michael Jacobs, Oracle's attorney, asked if a clean room approach doesn't protect against patents. Rubin said he didn't think so, but added he did not understand the question.

Jacobs also brought up e-mails covering the licensing of Java, specifically focusing on discussions between Rubin and Sun Microsystem's Vineet Gupta in February 2006 covering providing patent protection for Android.

"Had a long discussion with Eric [Schmidt, then Google CEO] tonight. He is cautiously skeptical if you and I can define the open-source license and include patent protection," Rubin wrote in the e-mail.

Jacobs also said, on another e-mail, that Rubin seemed to show concerns about using Microsystem's patents. Rubin responded by saying that he did not conduct a review during Android's development to investigate Sun Microsystem's patent portfolio. Google is expressing the message throughout the trial, claiming it had no knowledge of the patents.

Rubin was asked about the review in more depth, and he said he did a review on a more personal level before the case was filed in 2010.

Rubin wasn't the only person in the stand, however: Google engineers Tim Lindholm and Patrick Brady, along with Oracle's engineers Bob Vandette and Noel Poore, were called.

Jacobs added that Oracle isn't just suing Google for patent violation, but also indirect infringement on the part of the Android ecosystem and the OEMs that install Android on mobile devices.

"They are infringing, but we're holding Google responsible for that infringement because they put the code out there and have relationship with these partners," Jacobs added. Devices used as evidence could be HTC Evo, for example.