Inducing confessions, extorting confessions by torture (for the police) and colluding with confessions (for criminal suspects) are all illegal, and their testimony is invalid.
Even if there is no evidence to prove that the confession was induced or coerced, in court, as long as the criminal suspect and witness show that the testimony was made under coercion and inducement, not out of true will, the prosecution can not produce strong evidence. According to the principle that doubts are favorable to the defendant now, most courts will not accept the evidence of the prosecution. Therefore, in some cases, the defendant and the witness suddenly retracted their confessions, which led to the passivity of the procuratorate and the police.
Generally speaking, inducing confessions is related to extorting confessions by torture, including restricting personal freedom, threatening and other means to coerce witnesses or suspects to make confessions according to the meaning of the police/prosecution.