Why was it that Light's father could see Light's lifespan, while Mikami couldn't see it (which allowed him to deduce that Light was Kira)?


I was talking with a friend about Death Note and he said that he could't
understand one thing:

When Light's father died, he saw Light's lifespan with his Shinigami eyes, so
he could "confirm" that Light was not Kira. However, at the end of the story,
Mikami looked at Light with his Shinigami eyes and recognized him, because he
could not see his lifespan.

Is this actually a slight mistake in the story, or have I missed anything?
(It's probably the second one)




**In chapter 71** , Light was setting up a plan that would prove himself to be
innocent of being the killer (Kira); would give the NPA (National Police
Agency of Japan) the advantage over Mello; and would keep him safe if Mello
would ever get hold of his picture.

In order to kill Mello, he made preparations for a raid to take place at
November 10 at 23:59. Almost everybody in Mello's organization would die, but
in order to kill Mello himself he needed the help of the NPA. He sent them the
Death Note together with Ryuku, making it possibly for one of the NPA members
to bargain for the Death Eyes. He had expected Matsuda Touta to do the deal,
since it went with his character, but in the end it was his father, Soichiro
Yagami, who made the deal with Ryuku. With his father having the Death Eyes,
it would be impossible for him to be owner of any Death Note, and therefore,
he had relinquished ownership himself, instead of making Misa relinquish
ownership over hers. Also he knew it would be dangerous to be the owner of any
Death Note, since he knew Jack Neylon aka Kal Snyder had the Death Eyes and it
would be as easy for Mello to kill him as it would be for Light to find and
kill Kal Snyder. Of course, he was not going to stop being the killer (Kira)
soon, so to retain his memories he strapped Misa's Death Note to his body. By
doing so, he thought he would be able to kill Mello and prove himself innocent
once again for the NPA. He failed to kill Mello through this raid, though.

[![Light](https://i.stack.imgur.com/Fj4qMm.jpg)](https://i.stack.imgur.com/Fj4qM.jpg)

**In chapter 72** , you can see that in addition to what I said above, Light
also needed Ryuku to be there at the raid, to stop Sidoh from helping the
"mafia". He knew Ryuku would be so kind as to harass Sidoh a bit ^^.

[![Ryuku](https://i.stack.imgur.com/PEUA2m.jpg)](https://i.stack.imgur.com/PEUA2.jpg)

**In chapter 74** , you can see Light holding the Death Note when his father
dies. After an owner dies, the ownership will go to the first person that
picks up or touches the Death Note, and therefore Light becomes the owner
again.

[![Father
dies](https://i.stack.imgur.com/WHEAdm.jpg)](https://i.stack.imgur.com/WHEAd.jpg)

**In chapter 81** , Misa is ordered to relinquish her ownership to Teru
Mikami. At this point there are two human Death Note owners and they are Light
and Mikami, and Misa becomes an ordinary housewife. Therefore, Mikami is able
to identify Light as the owner of the Death Note and the real "Killer".

[![Misa](https://i.stack.imgur.com/k2CvPm.png)](https://i.stack.imgur.com/k2CvP.png)

For a summary of the Notes' owners the website provided by Maroon is really
useful. See [here](http://forums.animesuki.com/showthread.php?t=48148).




**In chapter 71** , Light was setting up a plan that would prove himself to be
innocent of being the killer (Kira); would give the NPA (National Police
Agency of Japan) the advantage over Mello; and would keep him safe if Mello
would ever get hold of his picture.

In order to kill Mello, he made preparations for a raid to take place at
November 10 at 23:59. Almost everybody in Mello's organization would die, but
in order to kill Mello himself he needed the help of the NPA. He sent them the
Death Note together with Ryuku, making it possibly for one of the NPA members
to bargain for the Death Eyes. He had expected Matsuda Touta to do the deal,
since it went with his character, but in the end it was his father, Soichiro
Yagami, who made the deal with Ryuku. With his father having the Death Eyes,
it would be impossible for him to be owner of any Death Note, and therefore,
he had relinquished ownership himself, instead of making Misa relinquish
ownership over hers. Also he knew it would be dangerous to be the owner of any
Death Note, since he knew Jack Neylon aka Kal Snyder had the Death Eyes and it
would be as easy for Mello to kill him as it would be for Light to find and
kill Kal Snyder. Of course, he was not going to stop being the killer (Kira)
soon, so to retain his memories he strapped Misa's Death Note to his body. By
doing so, he thought he would be able to kill Mello and prove himself innocent
once again for the NPA. He failed to kill Mello through this raid, though.

[![Light](https://i.stack.imgur.com/Fj4qMm.jpg)](https://i.stack.imgur.com/Fj4qM.jpg)

**In chapter 72** , you can see that in addition to what I said above, Light
also needed Ryuku to be there at the raid, to stop Sidoh from helping the
"mafia". He knew Ryuku would be so kind as to harass Sidoh a bit ^^.

[![Ryuku](https://i.stack.imgur.com/PEUA2m.jpg)](https://i.stack.imgur.com/PEUA2.jpg)

**In chapter 74** , you can see Light holding the Death Note when his father
dies. After an owner dies, the ownership will go to the first person that
picks up or touches the Death Note, and therefore Light becomes the owner
again.

[![Father
dies](https://i.stack.imgur.com/WHEAdm.jpg)](https://i.stack.imgur.com/WHEAd.jpg)

**In chapter 81** , Misa is ordered to relinquish her ownership to Teru
Mikami. At this point there are two human Death Note owners and they are Light
and Mikami, and Misa becomes an ordinary housewife. Therefore, Mikami is able
to identify Light as the owner of the Death Note and the real "Killer".

[![Misa](https://i.stack.imgur.com/k2CvPm.png)](https://i.stack.imgur.com/k2CvP.png)

For a summary of the Notes' owners the website provided by Maroon is really
useful. See [here](http://forums.animesuki.com/showthread.php?t=48148).

