According to The Law Dictionary
It is also necessary to prove that their slanderous words about you are all lies.
How does this make sense? Isn't it on the burden of a person making a claim to prove it's true? For example if someone is telling everyone I have been stalking them (and it's not true) how can I prove I didn't, can't I only ever disprove their evidence?
Defamation (Libel and Slander. See J. Jonah Jamerson for the difference between the two) is not a protected act of speech because it is speech used to harm someone on claims of actual damage. Since you are doing this in small claims, you simply have to file the suit in your local court to have the case go through (assuming you don't have a lawyer, who does this for you).
The Burden of Proof will depend on Jurisdiction. In the United States, speech is Protected Free Speech until proven otherwise, so you will need to prove this is a defamatory statement. You can get his evidence as to why he's making a truthful statement in the discovery process, but be willing to provide dates and times to show you were not there when he claims you were OR to show that you had a valid non-him related reason to be near him. Depending on how he is phrasing it, if you have not been convicted of stalking and he has not filed any motions against you in court, then you can use that to prove that this is false. If he has, he has the burden of proof to prove you are a stalker (although he doesn't have to say you are an alleged stalker... the media covering the case will say as such until proven guilty.. yes, even if the crime is caught on camera and it's definitely you, media writing rules still call the accused as such until proven guilty).
In the U.K. and other Common Law Jurisdictions, the burden of proof is on him to prove the claim is valid.
In addition, you need to prove that these charges have damaged you in some capacity. A loss of friendship, romantic encounters, housing or employment opportunities or membership to private club or service from businesses because of these untrue statements. At some part, you must show that his statements factored into a negative decision against you (probably to a significant degree).
Also be sure that these are statements of fact (OP is a stalker) and not belief/opinion (I believe OP is stalking me/ I think OP is stalking me) or hearsay ( The First Poster told me that OP is stalking me). The last two statements are technically true in that he has assessed the situation from his perspective and has come to this conclusion OR he is repeating a statement made to him by another source. Only the first statement is false.
Finally, in the United States, you need to prove malice on the part of the guy making the false claim IF you are a public or limited public person (a celebrity or a politician in the latter case, or someone who was temporarily a known person due to other matters like being related to another crime or news story that has put you into the press).
TL;DR:
It is Defimation if:
In the U.S. the burden of proof is on you (U.S. Only).
If you are a public entity (Politician, Celebrity, or subject of press coverage) you must prove intended malice towards you (U.S. Only).
Defamation (slander and libel) is a tort; often a crime, in other words you can become liable for defamation.
You can avoid liability for actions that normally are torts/crimes of you have a defense, or if there is an exception stated in the law.
For most jurisdictions, truth is an absolute defense/exception against accusations of defamation. The law may even say that it is enough to believe the claims are true. The Swedish Criminal code for instance states that damaging statements are not defamation if the claims are "true" or if the one making the damaging statements had "reasonable grounds" to believe they are true.
So here is where it becomes tricky: the defendant may therefore say...
"I thought that what I said about the plaintiff was true"
Can the plaintiff now prove — beyond reasonable doubt (in case of criminal tort), or the preponderance of the evidence (civil tort) — that this claim is false; that the defendant did not believe that and yet willfully said these things?
At this point the plaintiff can shoot down the defendant's defense by showing that the claims are lies.
Mallory (defendant): "Alice is a murderer that killed Bob!"
Alice (plaintiff): "Eh, no... because Bob is alive, he is sitting right there".
Bob: "Hi everyone!" waves
...but they do not have do that. It is usually enough to show that the defamatory claims have no reasonable grounds:
Mallory: "Bob is dead, and Alice killed him"
Alice: "Yeah, Bob is dead, we agree. But what do you base the claim that I killed him on? Do you have anything that points to me doing it?"
Mallory: "No, but I will assume you killed him anyway".
For most jurisdictions this is enough to convict Mallory for defamation.
So to answer your question: in order to successfully find someone liable for defamation, you must prove that 1) the statements are damaging to you and 2) either that the statements are false, or that the one that made the statements had no reasonable grounds for believing they are true.
It is a tort. You sue them. You go to civil court and say they harmed you and demand damages, such as forcing them to an action, bar them from an action, or the universal cure-all, heaping stacks of money. Jail is not an option.
It's likely you'll need to be in big court, small claims court won't want to touch it with a 10 foot pole.
Big court (at your level) is resolved mostly by intimidation games pre-trial, leading to a settlement, and no judge's gavel ever confirms your view of the facts. It's so sweet when it happens, but it's not very often, because trying in good faith to settle is mandatory,
Truth is a defense, so you don't have to prove they lied, but they will certainly raise the "it is true" defense, and your evidence that it is false must outweigh their evidence that it is true.
Unlike what you see on Judge Judy, this will get resolved 99% on paper. Standing at a podium talking to the judge will be about procedural matters, not facts. Unlike what you see on prime time TV, you're not allowed to drop surprise facts on the other side, that is a violation of court procedure and will get you sanctioned. (some places allow only the defense to do that in criminal trials only).
It varies a lot by jurisdiction exactly what elements must be present for defamation.
When you're working with the lawyer taking a hard sobering look at whether you can assemble all the case's requirements, you often find you cannot.
