Sentience is defined as an individual (human or otherwise) that understands all actions require the understanding of responsibility of the consequences of said action, and being able to justify action by environmental stimuli.
That is coupled with the understanding that each organism is potentially sentient.
One is only able to discern whether one is sentient by self evaluation.
One can only prove to another potentially sentient being that they are sentient by being a tedious communicator.
A tedious communicator is one who seeks the logos of each individual word communicated by the definition of the message's origination; either by common reference or agreed multi-party definition.
One in all situations has a time of choice.
Upon the time an individual relinquishes the ability to choose because of input from another potentially sentient being is the point in time when that individual becomes an undead communicator, or for the sake of definition, a "zombie".
A zombie is one who relinquishes control over their ability to take responsibility for actions one introduces by allowing a group to justify actions rather than an individual exploring their own reasoning.
A zombie is usually encouraged to "infect" other "non-zombies" by the Imposition of sentience.
Imposition of sentience is in all cultures this individual understands is a socially unacceptable practice. One can impose individual sentience by influencing other potentially sentient beings to perform actions by manipulation through logical fallacy, information control, or intended harm.
The way to perform "decapitation" of "zombies" is by relaying the fact that all concepts and objects exist simultaneously, despite an individual's polarization of understanding via zombification. Hence, the prevention of the imposition of sentience is of the utmost importance to every human being.