# How can a death note shorten the lifespan of others?

The use of the Death Note in the human world sometimes affects other humans' lives or shortens their original life span, even though their names are not actually written in the Death Note itself. In these cases, no matter the cause, the god of death sees only the original lifespan and not the shortened lifespan.

We saw, that Misas lifespan was shortened because Light was killed by Ryuk. So this means, that you can shorten a persons lifespan with the death note. So let's say, A has a death note and knows that C wants to kill B with a death note. He writes B's name in his death note, thus preventing him from being killed by a death note. So C, can't kill B with a death note anymore. But since the death note can shorten the lifespan of those, whos name isn't written in the death note, C decides to use Y, to set up a trap. C writes:

Y, Car accident. Dies at 12:30, after he produces a deadly poison, which he injects into the food the person he knows as ''B'' eats. After he did this, he will die 9 days later in a car accident.

So, could C shorten B's lifespan in this way, so that he is able to indirectly kill him?

• Writing B name in the DN prevents him from being killed by OTHER DN users. He will die in at most 23 days, killed by A's death note. Commented Jan 12, 2015 at 17:07
• This is not shortening B's lifespan indirectly. This is forcing Y to directly murder B, which is impossible. If C wanted B dead, he should just be a man and kill him the old fashioned way. Commented Jan 12, 2015 at 19:22
• @PeterRaeves "he should just be a man and kill him the old fashioned way" you said it. Commented Jan 12, 2015 at 19:37

Yes, to the extent of how can you manipulate a person's actions with the DN. (1) (2). But care must be taken not to break the other rules:

In your example, B will die in at most 23 days because A has written B's name in his DN.

But let's assume C wants B dead BEFORE that timeframe.

There is a conflict in the writing C did in the DN:

Y, Car accident. Dies at 12:30, after he produces a deadly poison, which he injects into the food the person he knows as ''B'' eats. After he did this, he will die 9 days later in a car accident.

C's writing may be in conflict with this rule:

If the death leads to the death of more than the intended, the person will simply die of a heart attack. This is to ensure that other lives are not influenced. Even though only one name is written in the Death Note, if it influences and causes other humans that are not written in it to die, the victim’s cause of death will be a heart attack

So it can either be considered as a violation of the rule above (and Y will die of heart attack) or work as intended by C.

It's not shortening B's lifespan, you had to write B's name in the death note to make that happen.

The way you can accidentally shorten someone's lifespan is, for example, killing the police officer that stopped B from getting shot, thus B's lifespan is implicitly shortened to the time where he gets shot.

• But why wouldn't it short his lifespan. Y would poison his food, which he knows, that B will eat it on that day. Commented Jan 12, 2015 at 16:06
• Because you have to write B's name into the Death Note, so you killed him with the Death Note, you haven't shortened his lifespan. Commented Jan 12, 2015 at 16:26
• @DarkYagami by writing B's name in your DN, you at most postponed C's plan by 23 days. Commented Jan 12, 2015 at 17:06
• @DarkYagami B's life cannot be influenced directly by another death note. So you need to be able to make a situation where you would write "Y shoots in the air 5 times" and then let the bullet land on B's head or let Y accidentally kill a loved one of B, which might force B to suicide, or something. The whole point of the rule is that you cannot write anything in the DN that would kill B with 100% certainty, because that would be directly killing him. Nobody knew for sure Misa would commit suicide, she could have lived a long and miserable life instead. Commented Jan 12, 2015 at 19:28
• @DarkYagami This is what she herself decided, but it was her own choice, unrelated to whatever was written in the DN. Commented Jan 12, 2015 at 19:29