Is it slander if you write something about someone that is the complete truth and can be backed up? How about a personal opinion that could or could not be true?

If you write something untrue its libel, not slander.

If its TRUE and you can prove it, then they may threaten you with a day in court but if you can prove the facts then you will win.

If you state that you are expressing a feeling, suspicion or personal opinion then you should be alright. Its when you have a bad opinion of someone and you express it as a fact, that it becomes libel.

"In my personal opinion it looks as though she is behaving like a lazy cow" - that's opinion.

"She is a lazy cow" - that's libel

Bascially, slander is an oral statement of or concerning the victim communicated to a third party that tends to lessen victim's reputation in the community.

Libel is a written statement satisfying the above criteria.

There are qualified privileges to slander and libel.

An issue to be considered is what are the vicitm's damages. Did the victim suffer monetary damages (special damages)? Generally speaking in order to file a lawsuit for slander or libel specal damages must be alleged in the complaint filed with the court. The exception being if the statement is slanderous per se. To read more: http://www.orangeinjurylaw.com/defamation.htm

Slander is an untruthful oral (spoken) statement about a person that harms the person's reputation or standing in the community. Because slander is a tort (a civil wrong), the injured person can bring a lawsuit against the person who made the false statement. If the statement is made via broadcast media -- for example, over the radio or on TV -- it is considered libel, rather than slander, because the statement has the potential to reach a very wide audience.

defamation in scotland covers written and oral - veritas ie truth is a defence

Slander is the spoken word and libel is the written word. It is very difficult to be awarded money by the courts for slander unless the complainant can prove that he or she has lost business or friends because of the slander. Proving that loss is difficult. In matters of libel, proof is not required by the court to show that the person who is libeled has actually suffered. The court will presume that the person has suffered. Recently, the Supreme Court of Canada has stated that even if a person has defamed another person by what he says to others or what he has written, if he honestly believed it to be true, then there is no just cause to be sued. The person defamed must satisfy the court that the person who defamed him did so with a malicious intent to harm his personal reputation or with indifference as to the truth or falsehood of the slanderous or libelous statement. Sometimes, that is hard to prove. In Canada, if you are approached by the person you have defamed and threatened with court action, you have the option of apologizing and correcting your statement in the same forum you originally made it. That generally resolves the problem unless the person defamed can prove that the damage is irreparable.

The difference between slander and libel is that libel is written down and slander is not. But where both converge is that they include an element of reporting something as being a fact. Opinion is different. For example, if I were to say "Santa Claus has been seen coming out of a gay nightclub with some of his elves, all dressed in short shorts", that is reporting as if it were a fact - and therefore slanderous or libellous. But if I were to say : "I think Santa Claus is gay" - that is my opinion. The thing about opinion is that it is true to the person stating it - but, as it is an opinion, it is open to others to interpret it according to their own viewpoint.

If it's true it's not slander but it could cause you some grief. It depends largely on why you wrote it. To read further go here:
http://www.infoplease.com/ce6/society/A0829656.html

False statements constitute as slander. That could include a personal opinion, because it can't be backed up as fact. A factual statement is not slander, by definition.

You cannot commit slander by telling the truth. You can commit slander when giving your opinion, if your opinion doesn't coincide with the truth.

I think it also depends on what you're trying to achieve. Just trying to make someone look bad, or actually trying to clarify something...

I'm no lawyer but I think its only when you say something that is false about the person. You would have to actually have proof you can see though for it not to be slander. Heard it from a friend ..who heard it from another that they were messing around is not proof.