We all know of miscarriages of justice where innocent people have been convicted.
Unfortunately it often seems your legal advice is dependant on how much money you have. This is an inherent failure of the justice system. Innocent people can and do get convicted of murder. Just look how many in the US who have been sentenced to death or life in prison, and are now exonerated. It is in the hundreds and most of them recent, all of them poor. Absolutely astounding.
A smart lawyer, some blurry forensics, and you walk away with blood on your hands.
Sad but true.
http://www.innocenceproject.org/know/