The second week of Oracle vs. Google kicked off this morning, with Andy Rubin making a brief appearance at the end of the day — but not before one of Google's attorneys grilled an Oracle technical expert, raising questions as to how thorough his investigation into the similarities between Java and Android had really been. Code-level comparisons between the two operating systems was the focus in general, starting with Square CTO Bob Lee. Having served as the core library development lead for Android for a number of years, Lee confirmed that Google engineers had referenced documentation from Sun when building the mobile OS "to make sure we were maintaining interoperability," and that when speaking with then-Engineering Director Steven Horowitz, "he said that yes there's lots of precedent for this, that's what we're talking about when we create a clean-room implementation."

Oracle followed Lee with Stanford Professor of Computer Science Dr. John Mitchell. Mitchell had analyzed the 37 APIs at the center of the case from both Java 2 SE 5.0 and Android 2.2 and found extensive similarities. In an attempt to further attack Google's clean-room claims, Mitchell also noted evidence that would seem to indicate Android code had been copied from a decompiled source: variables that would normally be given actual names for ease of use instead consisted of generic, machine-generated template terms such as "set Set1" and "boolean flag." Mitchell stated that he was even able to replicate the variable names by decompiling Sun code himself.

Oracle's expert wasn't familiar with Apache Harmony

The examples shown in the courtroom, however, all seemed to be copied from the Apache Harmony implementation of Java, rather than being the direct work of a compromised Google clean room. When pressed by Google counsel Robert Van Nest, Mitchell stated that he was actually not very familiar with Apache Harmony himself. Additionally, the report his own work was based upon — which included the comparison of thousands of files — yielded just twelve files containing similarities. Of all of the lines of comparable code, Mitchell was only able to positively confirm that nine lines made it onto shipping Android handsets — the nine lines that comprise rangeCheck.

Android head Andy Rubin took the stand late in the day, acknowledging that in 2005 Google had considered obtaining a TCK license for Android. He hedged when it came to an email he sent to Google co-founder Larry Page that mentioned paying for a license, however, stating that he assumed most manufacturers would already have such a license themselves. With almost all of Oracle's evidentiary emails either addressed to, sent by, or copying Rubin, his testimony may be the definitive word — from Google, at least — as to what the company's intentions were during the development of Android. Oracle is expected to wrap up its side of the trial's copyright phase tomorrow with both Rubin and former Google CEO Eric Schmidt scheduled to appear. We'll be there to bring you all the details.

Matt Macari contributed to this report.