The following is the case, A and B are how to criminalize, it is best to be more specific

Article 14 of the Criminal Law of the People's Republic of China **** and State Intentional crimes know that their actions will occur harmful to society, and hope or let such results occur, thus constituting a crime, is an intentional crime. In this case, Wu Zhe and Cheng Zhe poisoned Ma's food, and their subjective intent was to cause Ma's death, with a clear target. Therefore, Wu Zhe and Cheng Zhe constitute intentional homicide.

First, Cheng Mou mistaken sugar as arsenic, the fact that its behavior is unable to cause the death of Ma Mou, according to the "Chinese people's *** and the State Criminal Law" Article 23 Attempt to commit a crime has been embarked on the implementation of the crime, due to reasons other than the will of the criminals and did not succeed, is an attempt to commit a crime. Therefore, Cheng's behavior was an attempted intentional homicide.

For the attempted crime, the penalty can be mitigated or reduced according to the accomplished crime.

Second, Wu has used a sufficient amount of poison DDV, and Ma has taken the poison, but after Ma ate the poison, it produced repentance and was able to take Ma to the hospital to rescue. According to the Chinese people's *** and the Criminal Law of the State of Article 24 Suspension of crime in the process of the crime, automatically give up the crime or automatically and effectively prevent the results of the crime is a suspension of the crime.

For suspended offenders, did not cause damage, shall be exempted from punishment; caused damage, shall reduce the punishment.

Ma finally died in a car accident on the way to the hospital, does not affect Wu, Cheng's intentional homicide. It can only be done as a plot on the sentencing of the two of them.