There is no universal definition of a "speedy trial". Most districts set time frames but, they change from district to district.

In the case of Casey Anthony, there are several factors that could be involved in her case, such as attorney delays, court delays, statute of limitations, etc.

If she is still encarserated then there are several reasons for that:
She's either a flight risk or she couldn't afford to set bail, forfeit speedy trial is always a factor.

The source below is excellent on Florida Speedy Trial Law. You might want to take a look at that.

There is no simple answer to this question because when you stop and look at the cases the delays sometimes make sense. Of course, other times they don't. But, there is no simple amount of time that constitutes speedy.

Legally, some of the complicating factors include:
Each state is different. Some states use different amounts of time for different classes of crime.
Defendents often have the ability to "Waive" the right to a speedy trial in order to better prepare their defense.
Generally, also consider:
Circumstances beyond anyone's control can delay trials, and also new evidence can turn up requiring time consuming technical analysis.

Once the trial is ready to begin, it's pretty much up to the judge whether the trial is progressing reasonably and whether to grant delays to one side or the other.

I think that the delays are too large too often. But, I don't have a solution because modern trials for serious crimes are so complex.

The US Supreme Court has weighed in on the Federal Constitutional right in BARKER v. WINGO, 407 U.S. 514 (1972).
They unanimously pretty much said the same thing, ie., it depends:"Held: A defendant's constitutional right to a speedy trial cannot be established by any inflexible rule but can be determined only on an ad hoc balancing basis, in which the conduct of the prosecution and that of the defendant are weighed." They listed four factors to consider: " The court should assess such factors as the length of and reason for the delay, the defendant's assertion of his right, and prejudice to the defendant." In that case, a delay of 5 years was ok for a murder trial because the delays were for good reason and were not prejudicial to the defendant. (An accomplice was being tried first, but that trial went through six iterations.)

I think that if both the prosecution and the defense are proceeding in the best interest of their clients (prosecution and the people, defense and the accused) then the trial is considered speedy. Each may for reasons that are believed to be beneficial to the interest of their client ask for or create delays in order to do a better job of representing their client.

So as long as nobody is being held in jail while _absolutely_ nothing is done then a trial .. I feel .. would be considered to be going at the pace that would be legally considered speedy.