And then he goes to look at the note for a while. As Gil scans it, he shakes a little fingerprint powder on it, and shadows the impression of whatever was written on the page above the note. In this case, it's a drawing -- an amateurish facial study of a gagged blonde woman, with a tear spilling out of one eye.
Catherine confirms with the rest of the guys -- Sara is evidently still off having that coffee on Catherine -- that DNA confirmed the hair as belonging to Debby Reston. Gil points us all to the art -- which, in addition to its obvious Robert Crumb-like influences, also shows a similarly comix-influenced lack of proportion when it comes to head and limb size -- and says, "I tested the note with ESDA because I saw some indentations in the paper." Because this show sees no need to educate us on the actual forensics techniques used -- choosing instead to have characters like Warrick state the obvious with, "He must have written 'I HAVE HER' on an underlying page" -- I will tell you what ESDA is. The acronym stands for Electrostatic Detection Appartus, and it's one of two methods commonly used to recover indentations on sheets of paper. The paper with the latent writing is covered with a transparent material, which is fixed to the paper via vacuum drawn through an underlying porous bronze plate. This makes a tight covering-paper-plate sandwich, so the cellophane can prevent damage to the document. The sandwich is then subjected to a repeated high-voltage static charge, which creates a variably-charged surface; any impressions retain a heavier static charge relative to the flat paper. Black toner is then shaken over the surface, and it adheres to the charged area, effectively replicating the writing that caused the impression. The impressions are then photographed and preserved by covering the cellophane layer with an adhesive-backed clear sheet. As a result, the entire process is non-destructive to the original document.
Now that you know what ESDA is, now you also know that the CSIs used it to gaze upon some comix-inspired art. Catherine points out that prior investigations had concluded the killer was an artist or had some connection to the university's art department. Nicky notes, "Serials typically photograph their crime scenes. If we're dealing with an artist here, maybe he drew the crime scene instead." The CSIs all take a moment to thank their lucky stars they're not dealing with a macramé weaver. Then, because we haven't seen enough of this particular drawing, everyone analyzes it for a while. Warrick points out that it looks like the bound and gagged woman is in a small room. Gil wants to know what the small seat is in the foreground; Warrick thinks it's a chair or sofa. His interior design skills are tight, like his game. He's conscious of flow, and creating classic compositions balancing texture against shape. Oh, who am I kidding? Warrick is a shoe man. Nicky is the one you ask about interior design. Nicky notices the square window in the upper left corner, and after they blow it up, we see that it's backwards writing of some sort. Catherine figures it's some some sort of signage; Gil signals his contempt for the sign with, "The letters are backwards." Nicky dons the helm and mantle of alter-ego Snicky and says, "Cramped space, chairs in the foreground but no other furniture, no shutters or curtains on the windows. Maybe it's not a room. Maybe it's a vehicle."