Research postmortem evangelism. It is Biblical that souls in prison have been preached to before. Whether or not this is a regular practice that God does or if it is only for special circumstances I do not know either. This isn't a popular doctrine, but it's Biblical. Consider these verses:
Death does not separate us from God's love:
Romans 8:38-39
38For I am persuaded, that
neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,
39Nor height, nor depth, nor any other creature,
shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
The dead who have not heard the Gospel of Christ are given it in order for them to have a chance to be fairly judged:
1 Peter 4:5-6
5Who shall give account to him that is ready to
judge the quick and the dead.
6For for this cause was
the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the spirit.
The dead will also hear the voice of Jesus:
John 5:25,28
25Verily, verily, I say unto you, The hour is coming, and now is, when
the dead shall hear the voice of the Son of God: and they that hear shall live.
28Marvel not at this: for the hour is coming, in the which
all that are in the graves shall hear his voice,
The wicked who died in the days of Noah went to "prison" and later got preached to, after death:
1 Peter 3:18-20
18For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit:
19By which also
he went and preached unto the spirits in prison; 20Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water.