2. Collecting evidence should be purposeful and planned. In a murder case, we should first investigate the person who has a grudge against the owner, and gradually narrow the scope of suspects through investigation to determine the key suspects.
3. Collect evidence objectively and comprehensively. Objectivity means opposing preconceptions and subjective assumptions. Comprehensive, that is, it is necessary to collect evidence to prove that the suspect is guilty and to collect evidence to prove that the suspect is innocent.
4. Collect evidence in depth and in detail. In-depth and meticulous investigation and evidence collection is often different from superficial phenomena.
5. Relying on the masses and combining scientific and technological means.
Rely on the masses, because any crime will leave traces. Find more people to investigate, and the more clues you can collect, the more comprehensive you will be. Instead of telling the masses that they are suspected without trial, inciting people who don't know the truth to shout slogans and suppressing justice with public opinion. With the continuous development of science and technology, we should make full use of advanced scientific and technological means to obtain evidence and identify its authenticity.
6. Strictly abide by legal procedures and keep secrets. Strictly abide by legal procedures, and it is strictly forbidden to extort confessions by torture and collect evidence by threats, enticements, deception or other illegal methods.
7. Evidence must be fixed in time and properly kept.
Legal basis: Article 68 of the Civil Procedure Law of People's Republic of China (PRC), the parties shall present it in court and cross-examine. Evidence involving state secrets, commercial secrets and personal privacy shall be kept confidential. If it needs to be presented in court, it may not be presented publicly.