The US Court of Appeals for the Federal Circuit in Washington questioned Google's claim that Oracle does not own copyright over some portions of the Java programming language.
Oracle claims that Google has illegally incorporated some of the features of Java into its popular Android and Android infringes its copyrights by structuring 37 Java APIs.
Oracle sought the court to allow it pursue the case against Google claiming a compensation of over $1bn for developing its Android operating system using 'copied code'.
According to the Oracle lawyer Josh Rosenkranz, Google 'took the most important, the most appealing' parts of Oracle's Java programming language to create Android.
The latest case is being closed watched whether application programming interfaces, or APIs, shortcut tools deployed in software to carryout essential functions including connecting to the Internet, can be copyrighted.
In its appeal, the US application developer is making an effort to upend a judge's ruling that the Java's interfaces are not legally protected, which allows application developers to write programs that can operate across operating systems.
Google argued that Oracle cannot copyright the structure of Java as it is an open-source or publicly available software language.
Earlier the US District Judge William Alsup stated that the Java APIs used by Google were not subject to copyright protection and were free for all to use.