Here is a statement by the WTS about self-defense. This from the for-the-public Awake magazine.
Turning the other cheek does not mean that a Christian would not defend himself against violent assailants. Jesus was not saying that we should never defend ourselves but, rather, that we should never strike offensively, that we should not allow ourselves to be provoked to take revenge. While it is wise to retreat whenever possible in order to avoid a fight, it is proper to take steps to protect ourselves and to seek the help of the police if we are a victim of a crime.
Another from 2008:
Also from an Awake:
However, if an intruder was fatally struck at night, the householder could be exonerated because it would be difficult for him to see what the intruder was doing and to ascertain the intentions of the intruder. The householder could reasonably conclude that his family was under threat of harm and take defensive action.—Exodus 22:2, 3.
The Bible thus indicates that a person may defend himself or his family if physically assaulted. He may ward off blows, restrain the attacker, or even strike a blow to stun or incapacitate him. The intention would be to neutralize the aggression or stop the attack. This being the case, if the aggressor was seriously harmed or killed in such a situation, his death would be accidental and not deliberate.
Another Awake from 1991: