Truth and falseness are the premise and major theme of this play. One element of this exploration of truth and falseness is the role that film has as an indicator of truth though a product of fictionalization. While Francois is innocent, his experience with the polygraph test undermines his confidence in his knowledge of reality, which is even further undermined when he learns a film is being made to portray the actual murder.
In Polygraph by Lepage and Brassard, the theme of truth vs. falsehood is prevalent not only in David's search for the murderer, but also in his dishonesty—inferred by not sharing the polygraph results—as well as the truth of Francois' involvement in, or innocence of, the murder. While the falsehood related to David's behavior is easy to see, the truth of who murdered Francois' friend years before is never uncovered.
David and Francois who met during the proceedings of the inquest into the rape and murder of Marie-Claude-Legare in Quebec City, find themselves in the same circle again (six years later) through the character of Lucie, an actress who witnesses a suicide and gives a statement to David; she also happens to be Francois' next door neighbor. The three interact.
In discussion with Lucie about the unsolved case, David admits that even when someone passes the polygraph test, the authorities never give this information to the suspect. In fact, they withhold it purposely:
Poor Francois...At the Parthenais they know he is innocent, but he'll probably never be told.
In a police inquiry where the guilty party hasn't been identified, it's strategy to keep everyone in ignorance.
David admits that it was he who gave the polygraph to Francois—though Francois does not know this. David, however, recognizes Francois.
As the play progresses, Francois is said to walk "like a predator," in one scene. We hear his wailing and lamenting cries through the wall of the apartment (as does David). Francois has a terrible temper, lashing out at David for asking too many questions, sounding like an "interrogator in a bad detective movie." When Lucie asks Francois if he killed the girl, he admits:
I don't think so.
Lucie asks for an explanation; Francois says:
...sometimes...I don't know anymore.
Is he guilty?
David gives a psychological analysis of the process and effects of the polygraph on a suspect.We learn that in Francois' case, the polygraph "gave evidence that this witness was really telling the truth."
The witness was not told because the tester (David) wanted to see how the suspect would react without assurance of his innocence—maybe giving away hidden information. This infers, then, that the polygraph test can be "tricked." We know today that this is true...that intimidation by the tester can evoke unreliable signs of guilt. It has been suggested that polygraph results are not based on a reliable science.
And while David believes...
...such strategies...should be used only with great care and compassion [...because] the psychological response we trigger is so violent as to effect a lasting disorder in the mind of a totally innocent suspect...
...this was not a concern, it seems, in Francois' case.
A flashback shows Francois' response. Note the stage direction in italics:
(a complete emotional breakdown)
...I didn't kill her!! It wasn't me! It wasn't me! You want to drive me mad, that's it!! You are driving me mad...
...the police never told him he was released from suspicion...He was never let off the hook.
While David's professional behavior is standard procedure, this deceit does, in fact, damage Francois—by the end he is no longer sure of his innocence. He takes his life by throwing himself in front of a moving train; the audience can only wonder.
We see David's falsehood practiced on Francois—and its effect. We never know for certain, however, if Francois was innocent.