As for gang detention, it depends on whether they have any evidence to prove that your brother is an accomplice. If there is no evidence, they must release him within 37 days. Because it's the law.
There are three kinds of detention: criminal detention, public security detention and judicial custody.
1, longest public security detention 15 days.
2. The longest period of judicial detention is 15 days.
The longest period of criminal detention is 37 days. Decide whether to arrest or take other compulsory measures after the expiration of detention.
Legal basis: Criminal Procedure Law
Article 65 The public security organ shall interrogate the detained person within 24 hours after detention. If it is found that it should not be detained, it must be released immediately and a release certificate will be issued. Those who need to be arrested but have insufficient evidence may be released on bail pending trial or under residential surveillance.
Article 66 When a public security organ requests the arrest of a criminal suspect, it shall write a letter of approval of the arrest and submit it to the people's procuratorate at the same level for examination and approval together with the case file and evidence. When necessary, the people's procuratorate may send people to participate in the discussion of major cases by public security organs.
Article 67 The people's procuratorate shall decide whether to examine and approve the arrest of a criminal suspect. Major cases shall be submitted to the procuratorial committee for discussion and decision.
Article 68 After examining the cases submitted by the public security organs for approval of arrest, the people's procuratorate shall decide whether to approve or disapprove the arrest according to the circumstances. The public security organ shall immediately implement the decision to approve the arrest and notify the people's procuratorate of the implementation in time. If the arrest is not approved, the people's procuratorate shall explain the reasons, and if supplementary investigation is needed, it shall also notify the public security organ.
Article 69 If a public security organ deems it necessary to arrest a detained person, it shall, within three days after detention, submit it to the People's Procuratorate for examination and approval. Under special circumstances, the approval time can be extended by one to four days.
For major suspects who commit crimes on the run, commit crimes many times or commit crimes in collusion, the time for submitting for examination and approval may be extended to 30 days.
The people's procuratorate shall, within seven days after receiving the approval letter from the public security organ, make a decision on whether to approve or disapprove the arrest. If the people's procuratorate does not approve the arrest, the public security organ shall immediately release it after receiving the notice and promptly notify the people's procuratorate to execute it. Those who need to continue the investigation and meet the conditions of obtaining a guarantor pending trial or residential surveillance shall be granted a guarantor pending trial or residential surveillance according to law.
Article 70 If the public security organ thinks that the people's procuratorate's decision not to approve the arrest is wrong, it may request reconsideration, but the detained person must be released immediately. If the opinion is not accepted, it may be submitted to the people's procuratorate at the next higher level for review. The people's procuratorate at a higher level shall immediately review and make a decision on whether to change it, and notify the people's procuratorate at a lower level and the public security organ to implement it.