Is capital punishment not contradictory to this injunction of the International Covenant on Civil and Political Rights (ICCPR)?

Article 6:

"Every human being has the inherent right to life. This right shall be protected by law. No one shall be arbitrarily deprived of his life".

Cesare Beccaria, a philosopher living from 1738-1794, argues against the death sentence as a less effective deterrent than a long sentence. The following is a summary of his writing "On Crimes and Punishments (1764), taken from the Internet Encyclopedia of Philosophy: [http://www.utm.edu/research/iep/b/beccaria.htm]:

"... For Beccaria, history shows that capital punishment fails to deter determined criminals. What we know about human nature also suggests that it has minimal deterrence value. A steady example over a period of time is more effective in creating moral habits than is a single shocking example of an execution. Beccaria argues that perpetual slavery is a more effective deterrent than capital punishment. Since we should choose the least severe punishment which accomplishes our purpose (i.e.,deterrence), then perpetual slavery is the preferred mode of punishment for the worst crimes. From the spectator's perspective, observing perpetual slavery will have a more lasting impression than capital punishment. Perpetual slavery will also seem more terrible from the vantage of the spectator, than from the criminal himself."