One of the seminal cases in the securities area is Virginia Bankshares v. Sandberg, 501 US 1083 (1991).  The case sets out the standard for showing when an opinion not subjectively believed can be actionable.  The opinion was a rare securities case written by Justice Souter.  The issue is by the way back at the US Supreme Court.  See Omnicare, Inc. v. Laborers District Council Construction Industry Pension Fund.  

Justice Souter stepped down in 2009 so has not participated in most of the High Court's consideration of securities cases during the Obama Administration.  Nonetheless, the Justice remains busy and continues to influence the law.  He has been sitting by designation on appellate court panels, mostly in the First Circuit.  Thus, since 2009, he has participated in at least four securities cases:  Bricklayers and Trowell Trades Intern. Pension v. Credit Suisse Securities, LLC, 752 F.3d 82 (1st Cir. 2014) (fraud on the market); Mass. Retirement Systems v. CVS Caremark Corp., 716 F.3d 229 (1st Cir. 2013) (causation); Automotive Industries Pension Trust Fund v. Textron, Inc., 682 F.3d 34 (1st Cir. 2012) (scienter); FirstBank Puerto Rico Inc. v. La Vida Merger Sub, Inc., 638 F.3d 37 (1st Cir. 2011) (statute of limitations).  

He wasn't the author in any of the cases so we don't really have examples of his analysis.  It was, however, the case that shareholders/investors were on the losing end of three of the decisions (all but CVS Caremark). Still, Justice Souter's role in these types of cases holds out some intriguing possibilities.  He could find himself interpreting cases that he wrote.  Imagine an opinion that addressed the reasoning in Virginia Bankshares. Presumably if that were to happen, his views would be entitled to some "unique" deference.