Keep in mind that in any criminal case, the state has to prove that the defendant committed the crime charged beyond a reasonable doubt. A good defense attorney will work hard to make sure the defendant gets a fair trial. I consider a fair trial to mean the jury decides whether or not the defendant committed the crimes charged based on the evidence introduced at trial.
When there is extensive media coverage, potential jurors are hearing things that may not be admissible at trial. There are extensive rules about what evidence can be admitted, and what LE can and cannot do to search and seize evidence. Those rules are there after two hundred years of crime and legislation. The rules are there to make sure we don't have show trials where innocent people are falsely accused, or are railroaded based on their race, religion, or ethnicity. Many lawyers become defense lawyers because they are concerned about state overreach - it's not about the particular defendant, but about striving for a criminal justice system that is not discriminatory and protects the rights that all of us enjoy.
So in many high profile cases, there are always motions to try to keep the media out. This isn't to "hide" the proceedings, but rather to ensure jurors will decide the case based on the evidence that is presented at trial - not what the media reports for three years. It's more about the integrity of the process then about the specific defendant. FWIW I tend to lean towards more openness - I support cameras in the court room and broader public records laws. But I can understand why a lawyer might feel the need to argue that it is prejudicial to his client's case at trial.
