Touring the old Stasi remand prison at Hohenschönhausen several years ago, I once put precisely this question to the tour guide. "What happened to the guards and interrogators after the end of the Cold War?" I asked.

He shrugged. "Who knows?"

He was being glib, of course. We do know what happened to a great many of them. Their identities are not secret (in fact, a list of all Stasi employees in December 1989 has been passed around on the internet for decades). It's just that the fate you might have expected (or even desired) simply didn't happen for the overwhelming majority of Stasi employees and informants. Even the high-ranking ones.

The Ministry for State Security (MfS) as a bureaucratic organism ceased to exist on November 17, 1989, just a few days after the fall of the Berlin Wall. Its unpopularity, and its identification with the collapsing government of the Socialist Unity Party (SED), made it toxic and unsustainable. There was a short-lived attempt to reinvent it as the "Office for National Security" (Amt für Nationale Sicherheit, or AfNS). In its twilight, the AfNS busied itself, inter alia, with the hurried destruction of as much of its archives as it could burn, shred, or rip. This excited the opposition of citizens' committees throughout the GDR, who occupied AfNS offices in various cities, beginning with Erfurt on December 4, 1989, and culminating with the occupation of the East Berlin headquarters on January 15, 1990. With that occupation, the Stasi effectively ceased to exist. Its employees were terminated or transferred to other departments by the end of March. Still tottering along zombie-like as a bureaucratic line-item, the AfNS was finally abolished with German reunification on October 3, 1990.

The Stasi's most important physical remnant is the more than 100 kilometers of paper archives that it left behind. The employees of the Federal Commissioner for Stasi Records (Der Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik, or BStU) were given the task of protecting them, organizing them, and in some cases re-assembling them from their shredded remnants (the task of the so-called "puzzle women"). The BStU is also responsible for making the records available for inspection on a limited basis to researchers, journalists, and citizens who are the subjects of the files. The Stasi Files Act of 1991 said that the records could be used to "establish if [persons falling into certain categories of public office or public trust, such as political officeholders or lawyers] were employed as full-time employees or as unofficial informers of the State Security Service." In the aftermath of reunification, a new word was added to the German language. Joachim Gauck was the first Commissioner for Stasi Records; to be "gaucked" was to have one's background checked in the files. A number of prominent East Germans, including many involved in the reform movement before reunification, were gaucked and revealed to have been informers (called "IMs" or inoffizielle Mitarbeiter, "unofficial coworkers"). Ibrahim Böhme, a co-founder of the oppositional Social Democratic Party in the GDR, was one of hundreds of thousands of IMs. The fact that IMs were almost always referred to by their codenames in the Stasi records made positive identification of informants sometimes difficult. Many political figures, such as Christian Democrat Lothar de Maizière and Left Party politician Gregor Gysi, have been dogged for decades by partially-substantiated claims that they informed for the Stasi. Sometimes, though, deduction was easy: A reader might discover in their Stasi file an informant who gives the details of conversations that the reader had alone with their spouse, dispelling any doubt as to the identity of the IM. The opening of the Stasi files destroyed some marriages, family ties, and other close relationships.

Aside from the social and political legacy of the Stasi, its demise posed a serious legal challenge in Germany. There was, as I mentioned above, considerable ill feeling toward the former Stasi officers and their informants. They were publicly shamed and ostracized. But could they actually be prosecuted?

Spies operating in West Germany were prosecuted if they could be found. NATO civilian employee Rainer Rupp spied for the Stasi, was arrested in 1993, and served six years of a 12-year prison sentence. It is likely, though, that many spies were never caught and simply "went to ground," because the Hauptverwaltung Aufklärung (Main Directorate for Reconnaissance), the Stasi's foreign espionage department, was particularly effective at destroying its own records during the Peaceful Revolution of 1989-90.

High-ranking Stasi officers proved difficult to prosecute - sometimes because their worst crimes were not technically crimes at all, sometimes simply because they were old men by the time they were put before a German court. Initially convicted of treason, chief Stasi spy Markus Wolf (until 1986 the head of the HVA), was cleared by Germany's Federal Constitutional Court in 1995. He could not have committed treason, it was argued, because he was serving a different country. He later received a suspended sentence for his involvement in a number of other crimes during the Cold War, such as the kidnapping of an East Geramn defector out of Austria in 1962. Alexander Schalck-Golodkowski, Stasi officer and head of the "Commercial Coordination" office, which managed various dubiously legal (or just illegal) economic schemes to obtain foreign currency for the GDR, was convicted in 1996 of violating arms-dealing laws and given a short probationary sentence. Erich Mielke, the Minister for State Security from 1957 until 1989, was never prosecuted for his role as the leader of the Stasi. Instead, he was prosecuted for his involvement in the murders of two Berlin policemen in 1931, and released due to ill health in 1995 very shortly after being imprisoned.

(Continued in a comment below.)