Killed Not As A Consequence

 Regarding 4 death penalties the Torah adds ישמעו ויראו. Regarding the ben sorer u'moreh (21:20,) the עד זומם in Shoftim (19:20) the zaken mamreh (17:13) and a מסית in Reah (13:11.) The Gra points out that is due to the law that is by these four cases Beis Din announces the reason why the death penalty is being carried out (see Sanhedrin 89a, the Rambam generally rules it means to carry out the death penalty on the holiday when all are present but for adim zommimim he rules that Beis Din sends out letters, see Aeuch Hashulchan C.M. 38:7.) Why are these four sins singled out that for a public demonstration to stamp out these sins? 

The Ramban explains the ben sorer u'moreh did not do anything to deserve of the death penalty and he is killed " to discipline the public so that others will not stumble... as a protective boundary, so that their death serves as a remedy for others." The death penalty is administered purely in order to be a deterrent for sin not as a consequence of his actions. The Ramban continues that the same holds true for the zaken mamreh who is killed merely to stamp out disputes with the courts and the adem zommimim who are killed despite having not actually affected anything through their testimony and the מסית who is killed merely for encouraging false faith even if his efforts are unsuccessful. That is why it is these 4 examples that Beis Din announces the sin for it in the context of these 4 examples that Beis Din punishes the victim not as a punishment for the action but to prevent an outbreak of greater problems. One killed for their sin does not the news paraded around for their is no concern for a general breakdown in society but when the entire purpose of the punishment is למען ישמעו ויראו then it is a requirement. 

The Rambam (Adut 20:4) says עדים זוממים do not need התראה לפי שאין בהם מעשה . The Raavad asks that there are other cases of sins without an action and they still need התראה? Rav Moshe Soloveitchik explains that the Rambam means that the adim are not killed due to their "action" of giving testimony as the Ramban above noted, but are killed due to the label of עד זומם being given to them (שם בגברא.) In that case there is no need for an active warning. Rav Soloveitchik (his Son) points out that the same argument is followed in halacha for the other above instances of זקן ממרא, בן סורר ומורה, מסית as well that they do not need a warning (see Rashi Sanhedrin 71a, Sanhedrin 66, Mamrin 3:8.) The reason being the same, they are not being killed due to their actions but the action creates a status on the person of being eligible for the death penalty. A warning is needed to define an action, but not to establish a status on the individual. 

(The explanation for עד זומם is צ"ע to fit with the Gemarah BK 4b that lists עדים זוממים as a mazik indicating they are punished for the act of causing harm, but see Tosfos there.)