Google co-founder Larry Page has stuck to his guns in a San Francisco court, testifying that the internet giant did nothing wrong when it built the Android platform for mobile gadgets.
Mr Page returned to the stand on Wednesday to field questions in a trial over accusations by business software titan Oracle that Google opted to infringe on Java program copyright and patents instead of licensing code from Sun Microsystems.
"We did nothing wrong," Mr Page said as he duelled with an Oracle lawyer. "We are very careful about what information we use and do not use."
Mr Page, swapping standard Silicon Valley casual wear for a charcoal grey suit, light blue shirt and matching tie, held firm even when confronted with a key piece of evidence - an email from Android team engineers saying that Google should licence Java technology from Sun Microsystems for the Android project.
Google worked long and hard with Sun to work out a way to incorporate Java into a smartphone platform, but efforts failed and Google went its own way with Android, according to Mr Page.
"I think Sun, and now Oracle, needed something that actually worked," Mr Page said. "We had a closet full of Java phones that didn't work."
While Google would have preferred to collaborate with Sun, it invested in its own smartphone platform, according to the co-founder.
"Things like the iPhone didn't have Java at all and somehow magically got in consumers' hands," Mr Page said. "I don't think it mattered."
The chiefs of Google and Oracle were opening witnesses this week in a patent case aimed at Android software used to power smartphones and tablet computers.
Oracle is accusing Google of infringing on Java computer programming language patents and copyrights Oracle obtained when it bought Java inventor Sun Microsystems in a $US7.4 billion deal brokered in 2009.
Google has denied the claims and said it believes mobile phone-makers and other users of its open-source Android operating system are entitled to use the Java technology in dispute.
Google unveiled the free Android operating system two years before Oracle bought Sun.
Protecting and profiting from Java software technology were prime reasons for Oracle's decision in 2009 to buy Sun, according to evidence presented so far at trial.
While testifying on Tuesday, Oracle chief Larry Ellison said that Oracle had considered buying Palm or Blackberry-maker Research In Motion to get into the smartphone market but didn't follow through.
Under questioning at trial, Oracle chief corporate architect Edward Screven said that Mr Ellison and others at the company had considered using Java to build a smartphone platform but decided it wasn't feasible.
"Google's Android-Java clone had basically foreclosed the market from us," Mr Screven said.
Mr Screven went on to say that Sun had "lost its way" by the time Oracle bought it and that making money on Sun software available free was one of the ways to recoup the price paid by Oracle.
Part of the Google defence is that Oracle couldn't figure out a way into the smartphone market so is trying to leech off of Android's success by pressing claims regarding Java software that Sun made publicly available.
"If people could copy our software and create cheap knockoffs of our products, we wouldn't get paid for our engineering and wouldn't be able to invest what we invest," Ellison said during his testimony.
Mr Ellison, an experienced courtroom witness, exuded confidence on the stand while Mr Page seemed cautious and evasive, causing the judge to prompt him to directly answer yes-or-no questions.
The trial before US District Court Judge William Alsup could last as long as eight weeks if jurors find that Google did infringe on Oracle's intellectual property and a damages phase is needed.