A guilty plea can be used as a defense of innocence. The duty of the defense lawyer in criminal cases is to put forward the defense opinions on the defendant's innocence, minor crime, mitigated punishment and exemption from punishment; In the trial procedure of the case, if the defendant pleads guilty and pleads guilty to punishment, it belongs to the circumstances of a lighter punishment, and the defense lawyer can defend on the basis of the circumstances of a lighter punishment. Doing an innocent defense does not mean that you will be judged innocent. Similarly, innocent defense is the defense direction of lawyers, and there is no conflict between the guilty plea and the innocent defense. The lenient punishment system of pleading guilty is an important measure to comprehensively implement the criminal policy of tempering justice with mercy. That is, a case in which the criminal suspect or defendant voluntarily and truthfully confesses his or her crime, has no objection to the facts of the alleged crime, agrees with the sentencing opinion of the procuratorial organ and signs a written statement of settlement, may be dealt with leniently according to law.
 What conditions do we need to defend innocence?
 1. The defendant does not have subjective elements of crime. Crime is constituted either by intent or by fault. A crime with intention as the constitutive element of a crime does not constitute an intentional crime because the defendant does not have a subjective intention. A crime with negligence as its constitutive element does not constitute a negligent crime because the defendant does not have negligence. Neither intent nor negligence constitutes any crime.
 2. The defendant is not the subject of the crime. The crime must also meet the subject requirements of the criminal law. The subject of the crime must reach a certain age of criminal responsibility and have the ability of criminal responsibility.
 3. The evidence of the defendant's criminal behavior is insufficient. As the basic principles of criminal trial, such legal basic principles as "a legally prescribed punishment for a specified crime" and "an appropriate punishment for a specified crime", the Criminal Procedure Law has established the principle of presumption of innocence. The evidence can not form a complete evidence chain or the evidence chain is disconnected, which will affect the determination of the facts of the crime and should be defended for innocence.
 4. The procedure of the case handling organ is illegal. The evidence obtained in violation of legal procedures is difficult to guarantee its authenticity and impartiality, and it is very likely to make mistakes in proving the facts of the case.
 To sum up, suspects should entrust lawyers to defend themselves in court. In many cases, they can also apply for innocence defense. They should reasonably use legal means to safeguard their legitimate rights and interests. As long as they meet the legal conditions, they can apply for innocence defense. Since they apply for innocence, they should defend to the end. Article 15 of the Criminal Procedure Law of the People's Republic of China, if a criminal suspect or defendant voluntarily and truthfully confesses his or her crime, admits the facts of the alleged crime, and is willing to accept punishment, he or she may be given leniency according to law.