There’s a saying that loose lips sink ships. So can dead weight.

Goldman Sachs CEO Lloyd Blankfein, who just got himself a lawyer, may be facing the possibility of sinking, either because of his own words in April 2010 before the Senate Permanent Subcommittee on Investigations (PSI) or because his shipmates are distancing themselves in a legal version of every man for himself. Or both.

Recall that Blankfein emphatically told the subcommittee, “We didn’t have a massive short against the housing market, and we certainly did not bet against our clients.” The 650-page subcommittee report (PDF) presented on April 13, 2011, which cites Blankfein 79 times, begs to differ.

The report accused Goldman of trading against its clients by simultaneously shorting certain subprime mortgage securities (a.k.a. “cats and dogs”) while stuffing them into the collateralized debt obligations it sold. It also suggested that Goldman executives, including Blankfein, misled Congress in testimony surrounding the Abacus CDO, Hudson, Timberwolf, and other deals, by saying it didn’t have a big short.

The top lesson I learned before leaving Goldman in the wake of Enron was Goldman’s foremost internal policy is to protect Goldman. It’s also to protect the most powerful members. When cracks manifest in the corporate armor, those two policies are at odds.

The executives running Goldman are exceedingly wealthy, not least because when the firm faced its darkest hour and lowest stock price in years during the bank-created crisis of fall 2008, the government provided it billions of dollars in the form of cheap loans, FDIC debt guarantees, TARP, AIG make-wholes, and a late-night moniker change from investment bank to bank holding company, giving the firm access to excessive Federal Reserve aid.

On Monday, Goldman shares took a 6 percent beating during final and extended trading hours on the announcement that Blankfein had hired a lawyer, without waiting for specifics. The last time its shares hit a 106.51 level was in early 2009.

That kind of downward movement concerns the firm’s partners. So would a wide number of casualties. Securing a separate attorney is a way to divide the firm’s members, to keep from being summarily conquered.

You could look at Blankfein hiring external counsel as a normal prudent, legal move. But that’s naive, given the attorney he selected. Hiring a major criminal-defense lawyer is about more than the fear of a $550 million SEC wrist slap for bad documentation in the Abacus CDO. It’s about the real possibility of doing time.

Big-shot Washington defense attorney Reid Weingarten, of the firm Steptoe & Johnson LLC, has represented former Enron chief accounting officer Richard Causey (who pleaded out), former Rite Aid vice chairman and chief counsel Franklin Brown (found guilty by a jury on 10 counts of conspiring to falsely inflate his company’s value), and former WorldCom CEO Bernie Ebbers (convicted on nine felony counts by a jury). All three are in jail. Two of them, Ebbers and Causey, had undergone congressional panel investigations beforehand. Another of Weingarten’s clients, former Tyco counsel Mark Belnick, was acquitted, though Tyco CEO Dennis Kozlowski, who was not represented by Weingarten, was convicted and remains in jail.

This is not a great pack to be associated with. The outcomes for most of these guys weren’t great either.

Still, Goldman can use attorney independence to the firm’s advantage. Weingarten is coming in “fresh” to prove, if necessary, that Blankfein’s statement to the effect that the firm was engaging only in a “market-making” role, and thus not strategically betting against its clients, was not perjury, since it was true. And yes, a market maker can be on any and all sides of a trade. But that’s not the most pivotal point of consideration.

The case would go: for the specific deals delineated in the April report, did you knowingly create or enable a situation in which your clients were at a monetary disadvantage? The report time lines, trade volumes, and emails point to this conclusion, whereas Blankfein’s words are at odds with it.

I emailed Goldman Sachs spokesman David Wells to ask:

“Is this a preemptive move, or is there an expected or pending indictment in the wings? Will there be other members of Goldman similarly seeking external counsel?”

He referred me to a statement he issued earlier: “As is common in such situations, Mr. Blankfein and other individuals who were expected to be interviewed in connection with the Justice Department’s inquiry into certain matters raised in the PSI report hired counsel at the outset.”

This week in 1934, “public enemy No. 1” Al Capone was sent to Alcatraz, having already spent two years in an Atlanta prison for tax evasion. The charge that did him in was minor compared with the money he pillaged, but it nonetheless sunk him.

Blankfein may find himself in a parallel situation. If, as Wells indicates, the CEO hired outside counsel to deal with the PSI report, he may be considering the prospect of a perjury and related obstruction of justice charge.

But in Weingarten’s other major cases, the clients were charged with inflating books, committing fraud, or stealing money. His retention may indicate any federal case could revolve around more than the perjury and obstruction charges. It remains to be seen if an indictment is levied and, if so, whether Blankfein gets a Capone or a Belnick outcome.