Usually a few days before bail pending trial.

Bail pending trial is a criminal compulsory measure for criminal suspects and defendants in criminal proceedings. If a criminal suspect or defendant who has been released on bail pending trial constitutes a crime, the court will still make a judgment in the future. In judicial practice, if the defendant who has been released on bail pending trial is unable to apply probation after examination by the court, the court will generally decide to arrest the defendant first after the court session, so that the defendant who has been released on bail pending trial will be taken into custody immediately after the court session.

Under normal circumstances, bail pending trial is applicable to minor criminal cases, and most cases will be sentenced to non-custodial sentences such as probation or control, and will not be criminally detained or arrested.

However, if he is released on bail pending trial due to illness, the disease has recovered, or he has committed a serious criminal offence, or the circumstances and nature of the crime do not meet the conditions for probation, the court intends to impose a real sentence. Once the defendant knows that he will be sentenced to actual punishment through various channels, some defendants may abscond when the court informs him to receive the verdict. As a result, the criminal proceedings cannot be carried out smoothly, that is, the judgment cannot be served, and the defendant will be put into prison to execute the penalty, and the case will be suspended. In order to prevent this from happening, the court will detain and arrest the defendant in advance before the trial, so that the actual sentence can be easily executed later.

To sum up, minor criminal cases are generally not put in prison before the trial, but cases where the court intentionally makes a guilty verdict and actually punishes them. Many times, the court will put in prison in advance to facilitate the execution of the judgment.

Legal basis: Article 79 of the Criminal Procedure Law, the people's courts, people's procuratorates and public security organs shall not release a criminal suspect or defendant on bail for more than twelve months, and the maximum period of residential surveillance shall not exceed six months. During the period of bail pending trial and residential surveillance, the investigation, prosecution and trial of the case shall not be interrupted. If it is found that criminal responsibility should not be investigated, or if the term of bail pending trial or residential surveillance expires, the bail pending trial and residential surveillance shall be released in time. When releasing a resident who has been released on bail pending trial, it shall promptly notify the resident who has been released on bail pending trial and the relevant units.