Whether it is death that occurs suddenly or gradually, there will always be a last thought moment (that creates death-proximate karma) before rebirth, whose quality links the person to a corresponding plane of existence. It is difficult to tell what the deceased’s last thought was if there are no clear signs. However, even if death was so sudden that there was no time to Nianfo properly before physical death, the true last thought is the very thought some time after the consciousness had left the body, but right before taking rebirth – if rebirth was not ‘immediate’ in the individual’s case.
This is why Zhunian （助念）should go on after physical passing, as many do not take ‘immediate’ rebirths due to habitual attachment and great confusion, with the consciousness lingering around, possibly for up to 49 days. (Only those who have done great good, great evil, or who have practised Nianfo well can have swift rebirths in the higher realms, lower realms and Pure Land respectively.) In short, we must assume there is still potential to guide the deceased to Nianfo with Zhunian to reach Pure Land. We ourselves should, however, practise Nianfo well in everyday life to avert sudden death in the first place, by creating more positive karma to dilute negative karma, and to be well practised in case sudden death happens.