evidence showing such a connection to be known in the prior art. II The question is whether the PTO was obligated to utilize its expert knowledge to determine whether the connection was well known in the prior art. As the Supreme Court has recognized, “the primary, responsibility for sifting out unpatentable material lies in the Patent Office.” Graham v. John Deere Co., 383 U.S. 1, 18, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966). The assumption that PTO examiners will use their knowledge of the art when examining patents is the foundation for the presumption in 35 U.S.C. § 282(a) that issued patents are valid. See Microsoft Corp. v. i4i Ltd. P’ship, — U.S.-, 131 S.Ct. 2238, 2243, 180 L.Ed.2d 131 (2011) (quoting Am. Hoist & Derrick Co. v. Sowa & Sons, Inc., 725 F.2d 1350, 1359 (Fed.Cir.1984) (<HOLDING>)). Just as the PTO’s expert knowledge is the
holding that a party seeking to establish particular claims as invalid must overcome the presumption of validity in 35 usc  282 by clear and convincing evidence recognizing that the pto has special expertise in evaluating patent applications holding that  282 codified the common law presumption of validity based on the basic proposition that a government agency such as the pto was presumed to do its job citing morgan v daniels 153 us 120 124 14 sct 772 38 led 657 1894 the pto is a special tribunal intrusted with full power in the premises holding that maintenance and enforcement of a patent obtained by fraud on the pto can form the basis for antitrust liability holding that the statute in question served to modify prior common law and that the legislature was empowered to make such changes in the common law based on the public interest