united-states libel
Libel - imaginary situation: Name of Subject not at first known
<p>X writes a malicious statement about Y on the internet, for instance accuses Y of a crime. Real name of Y isn't known at this moment of time, but it becomes known later. Does this still qualify as libel?</p>

<p>Laws on libel vary by jurisdiction. However, in general a defamatory statement that can be identified as being about a particular person can be held to be defamatory. The person need not be named specifically if the person is clearly identifiable.</p>
<p>Note that there are several other requirements not mentioned in the question. The statement must cause actual harm to reputation, unless it is one of the limited category of statements that are &quot;libel <em>per se</em>&quot; This will often include an accusation of serious crime. In many jurisdictions the statement must in fact be false. At least in the US, the statement must be a statement of purported fact, not an opinion.</p>
<p>On the other hand, if a false statement is made that in fact harms reputation, it is not usually essential to prove that it was malicious. However, in some jurisdictions malice must be proven to obtain punitive damages.</p>
<p>If the person making the statement does not know who it is about, it may not be libel in some jurisdictions. For example if someone wrote:</p>
<blockquote>
<p>Whoever started the wildfire last week was guilty of arson and murder.</p>
</blockquote>
<p>and a month later the person who started the fire was discovered, that probably would not constitute defamation.</p>
<p>The classic common-law rule is that a statement must be &quot;of and concerning&quot; the plaintiff to allow the plaintiff to sue and win in a libel case. But what kind of proof will be accepted for this element varies.</p>
<p>If  the alleged defamer (X in the question) knows the subject only by a pseudonym, such as a pen name or an online username, and uses that pseudonym in a defamatory statement, and it is possible to establish a clear connection between the pseudonym and Y, then that statement will be just as defamatory as if X had used Y's legal name.</p>
<p>In the classic case of <a href="https://en.wikipedia.org/wiki/New_York_Times_Co._v._Sullivan" rel="nofollow noreferrer"><em>New York Times v Sullivan</em></a> the Times advertisement at issue said that &quot;the police&quot; did certain things and that &quot;Southern violators of the constitution&quot; did certain other things. Sullivan was the city commissioner in Montgomery Alabama generally charged with supervision of the police, and he claimed in his suit that all these statements were &quot;of and concerning&quot; him, since the police could not have done them without his approval, and that by &quot;Southern violators&quot; the ad meant the police.</p>
<p>The Alabama court accepted these claims. The libel judgement was overturned, largely  on other grounds. But the US Supreme Court wrote:</p>
<blockquote>
<p>We also think the evidence was constitutionally defective in another respect: it was incapable of supporting the jury's finding that the allegedly libelous statements were made 'of and concerning' respondent.&quot;</p>
</blockquote>
<p>(<em>Thanks to Nate Eldredge for reminding me that the US Supreme Court addressed this issue in this case.</em>)</p>
<p>See <em>Make No Law: The Sullivan Case and the First Amendment</em> by Anthony Lewis for a detailed account of the case, including the Alabama court proceedings and the full text of the original ad.</p>
