If they had in their heart the Spirit of Christ, and then have fallen away this scriptures are the answer.
26 For if we go on sinning wilfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,
27 but a certain terrifying expectation of judgment, and the fury of a fire, which will consume the adversaries.
28 Anyone who has set aside the Law of Moses died without mercy on the testimony of two or three witnesses.
29 How much severer punishment do you think he will deserve who has trampled under foot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit of grace?
AND,
4 For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit
5 and have tasted the good word of God and the powers of the age to come,
6 and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the son of God, and put him to open shame.
According to the above they have killed Christ to themselves, so I am certain that Christ is no longer in their heart