Criminal defendants are at a disadvantage for many reasons. One of them is that they are not entitled to take depositions of expert witnesses. Expert witnesses are persons purchased by one side of a controversy to given an opinion that supports the side of the person paying the fee. You can find an expert willing to say almost anything, so that what an expert says is often b.s. and intended to deceive and confuse. In civil litigation over $100 or so, a defendant has the right to find out by document production what other opinions the expert has given, what articles he/she has written and other important things about the expert. In criminal cases where the defendant's life is at stake, he/she is not entitled to this basic right, and the experts for the prosecution sneak up on the defendant and the defendant's counsel and get away more readily with lying, because the criminal defendant had no chance to take the expert's deposition, under oath, and pin him/her down in advance of trial. The trial then becomes an ambush where the expert is able to say almost anything to pin guilt on the defendant, and the defendant isn't even able to speak up in his own defense because few defendants are ever put on the stand. Thus, the person who knows what happened is seldom allowed by his lawyer to testify (because of the fear that the prosecution will twist the defendant's words around and make the defendant appear guilty) and the persons who do testify are the experts who were not at the scene of the crime when it was taking place, and have been hired to say whatever the prosecution wants the expert to say. This is a good insight to our criminal justice system. There are many things wrong with such a system, but people only find out about it too late, after they are caught up in it.