如果有兩人為同一件美國專利侵權訴訟案的共同被告，那能否先派其中一人去提無效調查，摸清原告主張專利有效的理由後，再由另一人接續提出另個無效調查、對原告的理由進行針對性攻擊而提高獲勝率呢?？答案是不行的！美國專利商標局（USPTO）專利審理暨訴願委員會（Patent Trial and Appeal Board，簡稱PTAB）於日前拒絕了由深圳市銀星智慧科技 (以下簡稱深圳銀星) 對iRobot所提出的接續在先無效調查的另一個專利無效調查申請 (Successive Petition of Inter Partes Review)，其判斷的主要依據為 2017年General Plastic v. Canon 一案中所確立的一系列判斷要素，認為此行為對身為原告的專利持有人相當不公平，故拒絕此後續的無效調查申請。
對於是否接受針對同一件專利的接續IPR無效調查請求，PTAB主要引用自2017年9月對於General Plastic v. Canon 一案判決中所確立的一系列判斷基準，其主要包含以下七點：
是否為同一請願人對於同一專利的同一申請專利範圍所提出的無效調查請求 (whether the same petitioner previously filed a petition directed to the same claims of the same patent)。
於前次無效調查請求提出的時刻、前請願人是否已知悉或應當知悉後無效調查請求中所主張的無效證據 (whether at the time of filing of the first petition the petitioner knew of the prior art asserted in the second petition or should have known of it)。
於後無效調查請求提出的時刻、前無效調查請求是否已經進行到專利權人提出初步回應、或是PTAB已決定是否接受對前無效案進行調查 (whether at the time of filing of the second petition the petitioner already received the patent owner’s preliminary response to the first petition or received the Board’s decision on whether to institute review in the first petition)。
於後無效調查請求中，請願人從得知無效證據到提出後無效調查請求的時間長度 (the length of time that elapsed between the time the petitioner learned of the prior art asserted in the second petition and the filing of the second petition)
請願人對於前後無效調查請求之提出時間間隔是否有合理的解釋 (whether the petitioner provides adequate explanation for the time elapsed between the filings of multiple petitions directed to the same claims of the same patent)
PTAB有限的資源考量 (the finite resources of the Board)
對於有在先訴訟情形的，提出無效調查請求的時間不能超過一年 (the requirement under 35 U.S.C. § 316(a)(11) to issue a final determination not later than 1 year after the date on which the Director notices institution of review)
另外，本案的法官之一，WILLIAM V. SAINDON於協同意見書 (Concurring opinion) 中更進一步建議加入第8個考慮要素：後案的請願人使否與前案請願人皆為所主張專利之相關訴訟的共同被告 (the extent to which the petitioner and any prior petitioner(s) were similarly situated defendants or otherwise realized a similar-in-time hazard regarding the challenged patent)，以更佳的判斷是否有上述投石問路的狀況發生。
