Last August, John J. O’Brien, who was once a highly regarded and well-liked partner in the celebrated M&A practice of Sullivan & Cromwell, pleaded guilty to four misdemeanor tax offenses. In the end, he pleaded guilty to failing to file taxes relating to $9.2 million in partnership income, for tax years 2003 to 2008. Earlier this week, O’Brien was sentenced. So is O’Brien trading Biglaw for the Big House? And if so, how long a sentence did he receive?