At first, the townsfolk don't believe that the killer had been caught, but once the town displays the dresses and the hair, they insist on seeing the murderer himself. Finally, the town judge agrees to showcase Grenouille. When he appears the crowd goes silent, thinking that this man cannot possibly be a murderer. Once Grenouille is returned to his cell, however, the crowd becomes angry and demands Grenouille's blood.
Remember the evidence we've already been given about the effects of Grenouille's perfumes (making people think he's in a hurry, or garnering sympathy). While this doesn't seem to be Grenouille's final perfume, it's evident that the crowd's reaction is due to Grenouille's purposeful use of a particular scent.
The proceedings against Grenouille move quickly due to overwhelming evidence and his free confession of guilt. When asked for a motive, Grenouille says simply that he needed the girls. He's subjected to torture and when his answer doesn't change, the judge deems him insane. In April, Grenouille is read the verdict, which states that he shall be executed within 48 hours. He will be hanged on a cross and his joints will be broken, and he'll be left to suffer and die.
Grenouille's trial and torture serve to put distance and difference between him and the general population. It's simply inconceivable to them that he just needed them for no reason, but they also never suspect the true reason why he "needed" them badly enough to kill them.
A priest is sent to hear Grenouille's confession, but gets nothing. Over the next two days, people come to see the murderer, and the guards enjoy booming profits. The guards don't allow anyone to enter the cell or offer Grenouille food, as they fear that someone will poison him.
Again, religion holds no meaning or power for Grenouille. We see how valuable of a prisoner Grenouille is, as his guards fear for his safety and know he must be kept alive in order to appease the crowd.
The parade grounds are readied for the execution. A scaffold is built, as well as a grandstand for nobles. Vendors stock up on their wares. Monsieur Papon, the executioner, has a squared iron rod built with which to strike the prisoner. The townsfolk prepare as though for a holiday, readying their finest clothes and arranging religious services for after the execution.
This is at once extremely morbid and somewhat humorous, as the execution is turned into what is nearly recognizable as a sporting or entertainment event. It's not simply the death of the murderer that's important, it's the spectacle of it.
At Richis' house, he forbids such preparations and feels disgust at the people's glee. Having been given Laure's hair and nightgown, he spreads them on her bed and keeps watch. He finds himself disgusted by the murderer and doesn't want to consider him a person; he only wants to see him perish.
In Richis's case, the narrator is drawing more comparisons between him and Grenouille. Like Grenouille, Richis doesn't want to consider another human being as a person; he simply wants power and control over him.