With the sixth-term Control Yuan set to conclude its mandate at the end of July, Taiwan's constitutional oversight body has been pushing out investigations at a rapid pace. Not all of them have held up well under scrutiny.
The latest flashpoint involves a formal inquiry urging prosecutors and courts to reconsider the conviction of Taiwanese businessman Cheng Wen-yi, sentenced to thirteen and a half years for manipulating shares of Tatung Company. The case has drawn sharp rebukes from Taiwan People's Party Chairman Ko Wen-je and legislator Huang Kuo-chang, who accused the commissioners of neglecting serious work in favor of ethically dubious conduct.
The criticism may be blunt. But the procedural problems here are real.
A Web of Undisclosed Conflicts
One of the three investigating commissioners, Lin Yu-jung, has openly acknowledged having no legal background. By her own account, she took up the case largely at the prompting of Chien Chien-jung — a former High Court judge who left the bench to practice law and now represents Cheng's interests.
That alone raises uncomfortable questions about what actually drove this inquiry.
The "expert" witnesses the commissioners consulted compound the concern. All three were connected to the defense: Cheng's own attorney, that attorney's father, and a lawyer Cheng had sought to engage during trial but whose involvement the court had already rejected. None of these relationships were disclosed. None triggered recusal.
An investigation report that cannot clear basic conflict-of-interest standards undermines its own conclusions before making them.
The entanglements go further. A second commissioner, Kao Yung-cheng, sits on the board of the Weiguang Foundation — chaired by the same Chien Chien-jung who steered the case toward the Control Yuan and has filed constitutional petitions on Cheng's behalf. That Kao participated without hesitation or disclosure is precisely the kind of conduct that makes the public distrust oversight institutions in the first place.
The Case Itself
The underlying facts are not simple. Cheng and three associates pushed Tatung's share price from NT$5.5 to NT$14.5 within six months, generating combined profits exceeding NT$3 billion. Cheng alone took home roughly NT$1.27 billion. The funds were traced to overseas accounts, though courts could not conclusively establish whether the money originated from China. Cheng's Chinese financial backer, Ren Guo-long, was never convicted — and fled Taiwan under warrant.
The commissioners contend that Cheng was fighting a legitimate proxy battle for corporate control of Tatung, not engaging in criminal market manipulation. They further argue that the High Court and Supreme Court failed to properly apply a reformed expert witness provision under the Code of Criminal Procedure — potentially compromising the defendant's right to a full defense.
The Supreme Court was unmoved. The defense, it found, had not specifically identified which legal principles the lower court misapplied or how. Sentencing was proportionate. The calculation of criminal proceeds was lawful. A subsequent petition for further review was dismissed as well.
The Constitutional Court went further, rejecting Cheng's petitions three times between March and May of last year. Its reasoning was straightforward: the courts' position — that expert opinions submitted by the defense are personal views, not admissible evidence — simply did not meet the threshold for constitutional adjudication.
Where the Control Yuan's Authority Ends
None of the commissioners' conclusions are binding on the courts. Like legislative rider resolutions that impose no obligation on the executive, Control Yuan investigation reports can recommend — they cannot compel.
That is not a dismissal of the institution's role. The Control Yuan has helped reopen genuine miscarriages of justice, including the cases of Jiang Kuo-ching, Cheng Hsing-tse, Hsu Tzu-chiang, and Su Chien-ho. Those precedents carry weight. Cheng Wen-yi may yet file a new petition for retrial on the basis of this report. Whether that succeeds will be the courts' call, not the commissioners'.
What the commissioners cannot do is replace judicial reasoning with their own. The Control Yuan's mandate rests on a foundational constraint: respect for judicial independence, and non-interference with the substance of adjudication. Insisting that courts should have summoned expert witnesses — when the Supreme Court has ruled this falls entirely within judicial discretion and constitutes an "adjudicative core matter" — crosses exactly the line the institution is supposed to observe.
An Institutional Credibility Problem
The question this case forces is a structural one. If a conviction upheld through three tiers of judicial review, and rejected three times by the Constitutional Court, can be reopened through a Control Yuan inquiry riddled with undisclosed conflicts — what does that say about the coherence of Taiwan's legal institutions overall?
The Control Yuan exists to check executive power and correct abuses of public authority. It is not an appellate court. It was never designed to backstop the judiciary.
When it attempts to do so — through a process that would not survive basic scrutiny in any courtroom — the damage extends well beyond one businessman's case. It reaches the legitimacy of oversight itself. （Related： Opinion | Taiwan's Prosecutor General Vacancy: A Test for Judicial Independence Under Lai ｜ Latest ）
