And Justice for all...

Shamelessly stolen from Glenn's blog. 2 studies (although it is more of the same):

Blacks and males not only receive longer sentences but also are less likely to receive no prison term when that option is available, more likely to receive upward departures, and less likely to receive downward departures. When downward departures are given, blacks and males receive smaller adjustments than whites and females. - from here 

And the other one:

A study of 300 simulated court cases shows that experienced judges, lay assessors, prosecutors, police officers, and lawyers make decisions and convict defendants differently depending on whether they are men or women and what the defendant looks like. Eyewitnesses to crimes are also affected by these factors. This is especially pronounced if there is an extended period of time separating the crime and the testimony.
[...]

Among other things, it was shown that judges and lay assessors both assessed and judged accused individuals of the same gender as themselves more severely than the opposite gender. On the other hand, prosecutors, lawyers, police officers, and law students, regardless of their own gender, evaluated male defendants more harshly than women defendants.

[...]

A study of eyewitnesses to a fictive crime shows that male perpetrators are judged more severely than equally violent female perpetrators. If two weeks goes by after the witnessing of the crime, gender plays an even greater role. A man will be judged even more sternly than a woman, which means that when our memory does not serve, we tend to remember more in accordance with the image, or stereotype, we have in our minds. - from here