in february 2012, yeh and the judicial yuan began investigating tsai ing-wen's ties to the former yu chang biologics company. though the judicial yuan ended its involvement that august, yeh's probe continued, aided by colleagues and ma hsiu-ru. as the yu chang case was pending, yeh turned his attention to lin hsi-shan's investments, resulting in his impeachment. yeh next participated in impeachment proceedings against taipower executives, then reviewed housing restrictions placed on people accused of crimes. in august 2012, yeh himself was investigated by the special investigation division of the ministry of justice. later that year, yeh received a petition to review the death penalty. in february 2013, he announced the control yuan's decision to censure the ministry of economic affairs for its failure to review contracts signed by china steel, which led to lin yi-shih facing accusations of bribery. the control yuan issued a verdict on the yu chang case in october 2013, deciding to censure tsai ing-wen. before he stepped down in 2014, yeh led a discussion on the statute of limitations for justin yifu lin, and helped lee fu-tien and lin chu-liang review the implementation of the communication security and surveillance act.