Google senior vice president Andy Rubin made yet another appearance inOracle v. Google at the U.S. District Court of Northern California on Tuesday afternoon.

Called by Oracle, the focus this time was to learn more about Rubin’s knowledge related to patents belonging to Sun Microsystems.

Right from the beginning, the tension in the courtroom bumped up a notch as Oracle attorney Michael Jacobs began his questioning. Similar to his first few appearances on the stand in this case, Rubin responded by evading most of the questions throughout his testimony.

When Jacobs commenced by asking sharply, in a few different ways, if a clean room approach doesn’t protect against patents, Rubin replied that he didn’t think so but that he also didn’t understand the question.

Continuing to rely on emails as core pieces of evidence in this trial, Jacobs pointed towards email discussions between Rubin and Sun’s Vineet Gupta in February 2006 about providing patent protection for Android.

In one message, Rubin wrote, “Had a long discussion with Eric tonight. He is cautiously skeptical if you and I can define the open source license and include patent protection.”

In another exchange with Gupta along the same thread, Jacobs commented that Rubin exhibited some concerns about Sun’s patents.

As one of Google’s defense strategies in this portion of the trial is to assert it had no knowledge about Sun’s patents, Rubin’s responses that he did not conduct any review during the development of Android to investigate Sun’s patent portfolio concurred with that strategy.

But when asked about this in more depth by Jacobs, Rubin said that he only did this on a personal level during the days just before the lawsuit was filed in 2010.

As Rubin was called during the last 15 minutes of proceedings on Tuesday, he will retake the stand on Wednesday morning at 7:45AM PDT.

The role of the mobile OEMs in Oracle v. Google

Rubin’s appearance on the stand wrapped up a whirlwind, although dry, day of proceedings as Oracle began its case during the patent phase of the trial. Oracle called up witnesses at lighting speed in comparison to the pace of phase one.

Tuesday’s roster consisted of Google engineers Tim Lindholm and Patrick Brady, Oracle engineers Bob Vandette and Noel Poore as well as video depositions from Android team manager Dan Morrill and Motorola’s Rafael Camargo.

At one point during proceedings, Judge William Alsup wanted to know more from both counsels about the importance of mobile OEMs and how those partners figure into this case.

Jacobs reiterated from his opening statements that Oracle is not only suing Google for patent violation on what it does with writing applications and internal testing, 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 relationships with these partners,” Jacobs explained. He offered some examples of devices running Android that could be considered evidence, including the HTC Evo, Motorola Droid, and Samsung Captivate.

Google attorney Robert Van Nest rebutted by first responding that “obviously, there needs to be prove of infringement before anything else happens.”

Van Nest further argued that because Android is an open source platform, the handset partners are free to change what they want and they don’t have to tell Google what they alter. Instead, all the mobile OEMs are required to do is pass a test to prove they meet performance standards.