U.S. International Trade Commission (ITC) Judge Thomas Pender said in Washington on Thursday that "clear and convincing means something to me," speaking about the legalities of determining whether a patent should or shouldn't have been issued.
"I have to be pretty darn certain a U.S. patent is invalid," Pender added.
HTC accused Apple of infringing two patents relating to 4G technologies.If Apple is found to have infringed HTC's patents, that could lead to a U.S. import ban on the iPad and iPhone 5.
After Apple sued HTC over iPhone patents in March 2010, the ITC's initial ruling came down in Apple's favor, stating that HTC had violated two of Apple's patents.
In 2011, HTC fired off its own patent lawsuit against the iPhone and iPad maker over Wi-Fi-related patents. HTC sought an import ban of Apple's line of Macs, iPads, iPods, iPhones, and other Wi-Fi enabled devices.
Earlier this year, HTC scored a victory over Apple at the U.K. High Court, after a judge ruled that three of the four Apple-owned patents in Europe were invalid. HTC was not found to have infringed the fourth patent, which related to photo management software.