Please understand evidence collection, qualitative or criminal law! !

You said that this matter has now been handed over from the traffic police to the criminal police, which means it has officially entered the criminal investigation stage. It is normal for other policemen to do what they do, but if they don't interrogate the suspect, there will be a problem. Compulsory measures must be taken against criminal suspects unless bail pending trial is handled. I can't draw any conclusions if you don't make it clear. There are seven kinds of evidence: physical evidence and documentary evidence; Witness testimony; The victim's statement; Confessions and excuses of criminal suspects and defendants; Appraisal conclusion; Records of inquest and inspection; Audio-visual materials. As long as you have one or more of the above items and can prove the facts, you can still be convicted and sentenced without witnesses. The period of investigation and detention of a criminal suspect after his arrest shall not exceed two months, which means that the criminal police should give you an answer within two months (this is another story). Now, if you think that the police have administrative inaction, you can lodge a complaint with the procuratorial organ or his superior organ, or you can directly file a criminal incidental civil lawsuit with the court (find relevant evidence yourself, but some evidence can't be obtained, for example, the traffic police's traffic accident inspection record can be applied to the court for extraction. )