The Oracle-Google Java trial marches on and on Wednesday, May 9, Stanford professor John Mitchell claimed Android infringed on two Java patents. Mitchell is a witness hired by Oracle.

The two Java-related patents are 6,061,520 and RE38,104. Oracle is paying Mitchell to take the stand. Judge William Alsup has criticised Google and Oracle for bringing in paid witnesses who simply agree with the companies' lines, as the trial entered its fourth week.

Oracle sued Google in 2010 and claimed the company broke copyright and violated the aforementioned patents when building Java for Android. Google avoided licensing Java by creating a virtual machine - called Dalvik - for running Java applications.

On Monday, May 6, the jury concluded that Google infringed on Oracle copyrights covering the overall structure sequence and 37 Java APIs. However, the jury was unable to agree on whether Google's use of the copyrighted material was fair use under law. Google argued infringement and fair use have to be decided simultaneously, though Alsup has not made both decisions.

The trail is now focusing on whether Google has violated Oracle patents.

The '104 patent covers the method of translating software code in a usable application. The patent uses "symbolic references" to identify data during compilation, which Oracle argues Google's virtual machine doesn't.

The '520 covers a way of consolidating classes of files for virtual machines execute less code. Oracle claims Google uses "simulated execution," while the search giant claimed it parses files.

Mitchell answered question from Oracle's lead counsel Michael Jacobs and explained diagrams and software code that proved Google's infringement. Additionally, Mitchell says he ran tests on Android prior to the case. In his view, the tests also prove infringement.

The jury has also been told to view Mitchell's claims as fact despite being paid by Oracle. Google will call its experts witness soon.

Oracle must prove Google intentionally ignored Sun Microsystems' patents when developing to dalvik virtual machine to prove infringement. Andy Rubin was called to court on Wednesday morning, May 9.

"As an engineer, you shouldn't study someone else's invention when you're trying to come up with our own," Rubin said when asked if he was aware of the Java patent portfolio.

(reported by Jonathan Charles, edited by Dave Clark)