Detective Wingate was called to Lab Tech Industries to investigate a murder. Lying on the floor of Lab D was Violet Robinson, dead from an apparent gunshot to the head. There were two drops of blood on her right shoe, her lab coat was missing one button, and the latex glove on her left hand had one small tear; but other than that, nothing seemed too noteworthy about the body. A small puddle of blood around the entry wound and a decanter on its side at the workstation were the only things out of place in the otherwise spotless laboratory. Lab supervisor James Bensen had found her at 7:42 am.

Upon arrival of the CSI team, Detective Wingate directed his attention to the employees that had worked with Violet the evening before. Each was interviewed separately from the others.

James Bensen was the first to be taken to the employee lounge for interrogation.
James: "I worked with Violet in Lab A last night for about 45 minutes. We completed our assignment, and she left. I assume she went back to Lab D where she usually works. That was at like 6:00 o'clock. I swear I didn't see her again until I came in this morning and found her laying there dead."
Detective: "When did you leave last night?"
James: "I left around 8:07 after my shift ended. I thought I was the last one out. The lights were all off."
Detective: "Why were you in so early this morning if you'd worked so late last night?"
James: "I am filling in for Adrian this week. She's our boss, and she's on vacation until Friday. I'm responsible for opening and closing the lab each morning and night. I can leave in between if I want, but we've been making some pretty important breakthroughs in endocraniological disorders; and I didn't want to miss any of it. If you have helped work on a project that has a major break-through, it can make your career."
Detective: "Do you guys always wear your lab coats and masks?"
James: "Yes. We must maintain a perfectly clean environment or our work could be contaminated by outside influences. We don't take them off unless we're in the employees' lounge or have exited the building."

Next, Detective Wingate spoke with Meggy Riddle, a janitor for Lab Tech Industries.
Detective: "Tell me what happened last night."
Meggy: "I had been cleaning in Lab D earlier in the evening, but when Violet started getting territorial around a project, I left. That was at maybe 7:15 or so. Dean went in after that, and I saw them arguing; at least I think it was Dean. I went to Lab F, which is kitty-corner from D, so I couldn't see perfectly. I cleaned in F until about 7:50 then cleaned G until 8:00 and left for the night. When I walked by the other labs, only Dean and James' lights were still on. They're in A and B. I was sure Violet had already gone home."
Detective: "How was Violet territorial?"
Meggy: "She got all weird about me being near her endocraniological diatrope testing. She started getting snotty, so I left. She and I don't get along very well, but that's no secret around here. She doesn't get along with most everyone."
Detective: "Tell me about the argument you witnessed between Violet and the other individual."
Meggy: "I could see them arguing through the window. Violet got so mad she picked up a heavy decanter and tried to hit him over the head with it. He stepped back, and she ended up missing. Then he just blew her off and went down the hall toward his lab. When he came out the doorway and turned to go down the hall, that's when I saw him, and I'm sure it was Dean."

When Dean Falcone was interviewed by Detective Wingate, he was adamant that he had not set foot in Lab D.
Dean: "I worked from 3:00 to a little after 8:00 without a single break. I didn't work with Violet last night and didn't even talk with her other than to say hello when I passed her once in the hall. I was never in Lab D. I don't know what Meggy is talking about. When I left, only James was still here."
Detective: "I heard you and Violet sometimes butt heads."
Dean: "Only because she gets so possessive about the projects. She thinks she should get all the credit in a major discovery. I have argued with her a lot, but not since last week; and certainly not last night! I swear it."

When the CSI completed their investigation of the crime scene, they called to tell Detective Wingate that Violet's prints were found on the decanter in Lab D. The decanter was otherwise clean. Was Meggy telling the truth about the confrontation between Dean and Violet? Detective Wingate didn't think so and ordered the arrest of Meggy Riddle. Why?