The work itself is more or less safe, but if you’ve ever put away a dangerous criminal or member of the mafia and they escape or get out on parole... better watch your back, buddy. They might file a Motion to Shoot You in the Back of the Head.
Other than that negligible concern, there are just the usual hazards associated with spending a lot of time gazing into a computer monitor - eye strain, soreness in your neck or back. Fortunately, however, most lawyers aren't as chained to their desks as other office professionals. They are taking meetings, showing up in court, or giving their eyes a break by looking through actual books from the legal library. By the time you read this, legal libraries may no longer exist - we're pretty sure the Kindle is working on that.