Terence Blacker: Do these trials serve the truth?

During rare interludes when a public inquiry is not on daytime TV, it is instructive to look at clips from the House Committee on Un-American Activities of about six decades ago, when it was under the chairmanship of Senator Joe McCarthy.

The focus of the respective investigations may be different – banking, journalism and Jimmy Savile take the place of McCarthy's search for "Communistic activities" – but there are unmistakeable similarities in tone. A powerful atmosphere of social disapproval attends the hearings. Questioning can be showily aggressive and sanctimonious. Sometimes it can seem as if discovering the truth is secondary in importance to humiliating the person under cross-examination.

No one could deny that inquiries, judicial or parliamentary, can make for great TV. Suddenly highly paid, privileged people are like schoolchildren summoned to headmaster's study. We have become sophisticated at watching these new Courts of the Star Chamber, and know every move: the faltering voice, the swivelling eyes, the general air of clammy panic.

What the McCarthy hearings showed, though, was that, in a febrile atmosphere of paranoia and moral panic, the truth tends to become skewed. As the broadcaster Ed Murrow said at the time, congressional committees could be useful but there was "a thin line between investigating and persecuting".

Such is the pressure, the charged atmosphere, which now attends inquiries that it affects the way evidence is given. Some public figures are strong and arrogant enough to show little respect to proceedings. Others, most recently George Entwistle this week, can appear weak, timid or indecisive when they are simply trying to be honest. On this type of reality show, the blusterers fare better than the mild-mannered.

Televised inquiries fuel public cynicism, and sanction a new form of bullying. Their popularity has as much to do with retribution and entertainment as with any search for truth.