<p>Just reread the manga and it turn out it was the police, probably with L help, that concluded the fact that Kira need both name and face</p>
<p>from Death Note Chapter 11 One, page 5</p>
<blockquote>
<p>Matsuda: He needs to know names? Is that true? I've heard he only needs to know the face</p>
<p>Chief Yagami: Criminals whose names were either wrong or kept hidden survived some mass killings, so the headquarters came to that conclusion</p>
</blockquote>
<p><a href="https://i.sstatic.net/CDcdK.jpg" rel="noreferrer"><img src="https://i.sstatic.net/CDcdK.jpg" alt="Death Note Chapter 11" /></a></p>
<p>L didn't do the stunt on tv with Lind L. Tailor to prove that Kira needs both name and face. But rather to prove that Kira exist, can kill people without being nearby, and live in Kanto area in Japan.</p>

CC BY-SA 3.0
2016-08-21T11:35:18.120Z
2016-08-22T09:27:08.280Z
2020-06-17T09:17:53.303Z
Darjeeling
<p>Even before the stunt on tv, L deduced an <strong>assumption</strong> that Kira needed the names and faces of a person to kill him. L came to that <strong>assumption</strong> by analyzing the people who were killed so far. All of them appeared on media either through tv or newspaper. This assumption was even more proved when Lind L Tailor was killed in the public TV stunt.</p>

<p>To answer your question, using this as a confirmation , L deduced that Kira needs a name and not just a face to kill someone.</p>

<p>Hope this suffices. </p>

CC BY-SA 3.0
2016-08-19T06:54:31.300Z
While you preface well, it might be helpful to actually link the answer back directly to the question (i.e actually answer the question than leave it implied)
Tyhja
CC BY-SA 3.0
2016-08-19T10:33:25.540Z
I thought by saying "his assumption was proved" i would have answered the question.
Bej
CC BY-SA 3.0
2016-08-19T14:42:49.280Z
But Kira could kill Lind L Tailor just by looking at his face and not actualy reading his name, right?
Zereges
CC BY-SA 3.0
2016-08-19T22:26:42.263Z
Well this is kind of my question. Kira kills Lind L Tailor, how does L know he even needed the name? The name and face was provided there, but how does L know that Kira needed both?
Rip Steel
CC BY-SA 3.0
2016-09-13T04:22:55.800Z
@RipSteel he does it by trial and error. It is like playing Sudoko, you don't directly know that a number belongs in its box but by deducing that it cannot be other boxes than this.
Bej
CC BY-SA 3.0
2016-08-19T06:30:50.777Z
2016-08-19T10:35:09.190Z
2016-08-19T10:35:09.190Z
Bej
<p>When the fake L went on live TV they put his name there. This was one of the major hints that Light needed a name and a face.</p>

CC BY-SA 3.0
2016-09-13T19:42:15.240Z
That is a hint, but not enough as *evidence.* The face could have been enough at that point since they never performed (nor could have performed) the cross-validation of face only.
Jan
CC BY-SA 3.0
2016-09-13T03:01:17.263Z
2016-09-13T03:01:17.263Z
Itachi Uchiha
<p>This is something that I've been wondering about, how does L deduce that Kira needs a name? Surely all the victims he investigated had their name and face, but how can he figure that he needs both? The stunt on tv with Lind L. Tailor only proved that Kira can't kill anyone, and there are certain criteria. I'm not sure how that concludes that he needs both name and face.</p>

<p>Edit: To clarify, here's how I look at it. L analyzes all the victims of the Kira killings and noticed that what was broadcast about the criminals was their face and their name. How does he conclude that Kira needs both? Why not just a face? When Kira kills Lind L. Tailor, that only validates that Kira has the ability to kill people, to which L himself even says "I couldn't believe it until I saw it, but it appears you can kill without being there in person." When Kira subsequently is unable to kill L, L can then deduce that there are people Kira can't kill. However he concludes Kira needs both name and face, which I don't understand. To me, at that point 3 conclusions are viable: Kira needs a name AND a face. Kira needs just a name. Kira needs just a face.</p>

CC BY-SA 3.0
2016-08-20T17:05:32.333Z
Re-reading the manga, I find that your question was correct and I remembered the details of the events wrongly. I thought L taunted Kira to kill him before revealing Lind L. Taylor's name. Apparently the name was visible from the beginning. +1
絢瀬絵里
CC BY-SA 3.0
2016-08-20T18:59:01.053Z
Hypothetically he may have deduced it but later he came to conclusion. Just like in episode 3 where he said "I want to know if the photos of the victim were made public" to the task force to make sure that his hypothesis is correct. And when few detectives came to know that L was right then those 3 detective resigned from that task force.
Light Yagami
<death-note>
How does L deduce that Kira needs a name and not just a face?
# How does L deduce that Kira needs a name and not just a face?
Posted by: username_0 on 2016-08-19
This is something that I've been wondering about, how does L deduce that Kira needs a name? Surely all the victims he investigated had their name and face, but how can he figure that he needs both? The stunt on tv with Lind L. Tailor only proved that Kira can't kill anyone, and there are certain criteria. I'm not sure how that concludes that he needs both name and face.

Edit: To clarify, here's how I look at it. L analyzes all the victims of the Kira killings and noticed that what was broadcast about the criminals was their face and their name. How does he conclude that Kira needs both? Why not just a face? When Kira kills Lind L. Tailor, that only validates that Kira has the ability to kill people, to which L himself even says "I couldn't believe it until I saw it, but it appears you can kill without being there in person." When Kira subsequently is unable to kill L, L can then deduce that there are people Kira can't kill. However he concludes Kira needs both name and face, which I don't understand. To me, at that point 3 conclusions are viable: Kira needs a name AND a face. Kira needs just a name. Kira needs just a face.
**Tags:** death-note
> **Comments:**
> **username_1**: Re-reading the manga, I find that your question was correct and I remembered the details of the events wrongly. I thought L taunted Kira to kill him before revealing Lind L. Taylor's name. Apparently the name was visible from the beginning. +1  
> **username_2**: Hypothetically he may have deduced it but later he came to conclusion. Just like in episode 3 where he said "I want to know if the photos of the victim were made public" to the task force to make sure that his hypothesis is correct. And when few detectives came to know that L was right then those 3 detective resigned from that task force.  
---
## 3 answers
### Answer by username_3 on 2016-08-21. Score: 14
Just reread the manga and it turn out it was the police, probably with L help, that concluded the fact that Kira need both name and face

from Death Note Chapter 11 One, page 5

> Matsuda: He needs to know names? Is that true? I've heard he only needs to know the face
>
> Chief Yagami: Criminals whose names were either wrong or kept hidden survived some mass killings, so the headquarters came to that conclusion

[![Death Note Chapter 11](https://i.sstatic.net/CDcdK.jpg)](https://i.sstatic.net/CDcdK.jpg)

L didn't do the stunt on tv with Lind L. Tailor to prove that Kira needs both name and face. But rather to prove that Kira exist, can kill people without being nearby, and live in Kanto area in Japan.
---
### Answer by username_4 on 2016-08-19. Score: 1
Even before the stunt on tv, L deduced an **assumption** that Kira needed the names and faces of a person to kill him. L came to that **assumption** by analyzing the people who were killed so far. All of them appeared on media either through tv or newspaper. This assumption was even more proved when Lind L Tailor was killed in the public TV stunt.

To answer your question, using this as a confirmation , L deduced that Kira needs a name and not just a face to kill someone.

Hope this suffices.
> **Comments:**
> **username_5** (2016-08-19): While you preface well, it might be helpful to actually link the answer back directly to the question (i.e actually answer the question than leave it implied)  
> **username_4** (2016-08-19): I thought by saying "his assumption was proved" i would have answered the question.  
> **username_6** (2016-08-19): But Kira could kill Lind L Tailor just by looking at his face and not actualy reading his name, right?  
> **username_0** (2016-08-19): Well this is kind of my question. Kira kills Lind L Tailor, how does L know he even needed the name? The name and face was provided there, but how does L know that Kira needed both?  
> **username_4** (2016-09-13): @RipSteel he does it by trial and error. It is like playing Sudoko, you don't directly know that a number belongs in its box but by deducing that it cannot be other boxes than this.  
---
### Answer by username_7 on 2016-09-13. Score: 0
When the fake L went on live TV they put his name there. This was one of the major hints that Light needed a name and a face.
> **Comments:**
> **username_8** (2016-09-13): That is a hint, but not enough as *evidence.* The face could have been enough at that point since they never performed (nor could have performed) the cross-validation of face only.  
---
