Google executive chairman Eric Schmidt was in court yesterday defending Google’s use of Java in its development of Android. The trial, which is in its seventh day, is over whether Google illegally used Oracle’s intellectual property when it used Java to develop the Android smartphone operating system.

In his testimony yesterday Schmidt said that Android was based on a “clean room” version of Java that did not use any of the code on which Sun Microsystems (later bought by Oracle) held any copyrights or patents. This, Schmidt said, came after negotiations between Google and Sun to partner for Android development fell apart due to Google’s insistence that Android remain open source.

Schmidt said that he was told during the development process that Android “did not use Sun’s intellectual property,” and that he “was very comfortable that what we were doing was legally correct. He also insisted that Sun had full knowledge of what Google was doing with Android and never objected or asked for a licensing agreement concerning Google’s use of Java. Schmidt – himself formerly the CTO of Sun – said that he met with Jonathan Schwartz – Sun’s CEO – regularly and that Schwartz never objected to the way Google was developing Android with Java.

While Oracle admits that Java is a programming language and thus freely available, they insist that Java’s APIs are their own intellectual property, and that to use them, Google needed a license. Oracle contends that Google knew this, and went ahead with development anyway. Google insists that the APIs can no more be copyrighted than the programming language itself, and that Google did not need a license to use them. The APIs, Schmidt argued during his testimony, are necessary to “make something happen” with the programming langage, and that “the Java language is not useful without the ability to make something happen.”

The trial is currently in its seventh day. Each side has scored points in its examination of witnesses. Oracle CEO Larry Ellison found himself ill-prepared to take the stand last week, while Google CEO Larry Page was evasive on the stand about whether Google needed a license to use Java.

In all, the trial is expected to take about eight weeks. If Oracle wins, it could cost Google as much as a billion dollars in damages and, perhaps more importantly, force Google to re-write the Android OS.