Prison guards have been accused of a number of Pittsburgh felonies - including sexual assault, sexual harassment, orchestrating assaults, and contaminating inmates' food.

Our Pittsburgh criminal defense attorneys understand that these are very serious allegations. However, even as the Pittsburgh Post-Gazette is reporting, these type of cases present a host of challenges for prosecutors.

The state's prison system is one that employs about 16,000 people and incarcerates more than 50,000.

At first, the charges against seven officers seemed outrageous. Collectively, they were charged with nearly 190 counts of abuse that included institutional sexual abuse charges. The cases garnered the national spotlight, and even spurred a civil rights investigation by the federal Department of Justice.

Guards were accused of urinating and defecating on the beds of inmates. They were accused of ordering sexually assaults, and in some cases, personally carrying them out. They were accused of ordering the physical assaults of inmates who had been convicted of sexually deviant offenses.

But what has happened since then has exposed giant holes in the case. In fact, there has been no physical evidence to back any of this up. That means no audio tapes, no video surveillance, no documents that supported any of it. Surely, given the huge scope of the allegations, if any of it were true, there would be something, right?

In fact, the newspaper conducted its own investigation and found that many of the accusations hinged on second-hand accounts. They weren't affirmed by the alleged victims. Or if they were affirmed, inmates later recanted, saying they had been pressured by investigators.

The main issue that arises here is the credibility of the witnesses. In one case, a prison guard's accusers are a robbery, a mentally challenged man and a sex offender. Certainly, that's not to say it is impossible that any of these acts occurred - but to what extent can they be proven?

It is the prosecution's job to ensure their case is airtight. But almost no criminal case is immune to cracks - and this one seems full of them. Even if there is evidence presented, a skilled criminal defense attorney can help a jury reach a conclusion of reasonable doubt.