Disclaimer: I do not own CSI or the character Gil Grissom. I am not making money off this story, so don't sue me.
Anna turned and walked towards the door. As she passed her boyfriend, Jacob, she gave him a smile for good luck, and he blushed in return. "If you're done flirting Mr. Clark, perhaps you'd care to pass this class."
Jacob blushed even more, and hurried up to desk. "Mr. Clark, is there a reason why you didn't turn in a paper over the process and evidence of dusting for finger printing."
"Sir," he explained, "my computer crashed and my paper was deleted."
"Does that excuse mean you know how dust for fingerprints?" Grissom countered.
"Yes sir."
Grissom opened the case again and took out a brush, and a container of black charcoal powder. Turning to the white board, Grissom said, "Find the prints."
Jacob picked up the brush and lightly dipped it in the charcoal powder. Stepping up to the white board, Jacob lightly turned his hand back forth, causing the brush to move back and forth over the board. As he worked, Grissom asked him, "How is the powder finding the prints?"
"Sir," without stopping, Jacob stated, "Fingerprints contain oils. The powder is being brushed over the prints and the oils are causing the powder to stick to the prints, thus outlining the individual characteristics of the prints. For example, three characteristics are arches, whirls, and loops."
"Why would someone look for prints?"
"No one in the world has the exact same fingerprint as another person. If a fingerprint found at a crime scene is identified, then you will be able to tie the fingerprint owner to the scene and maybe have enough for a warrant to gather more evidence. Sir, I found four prints."
"Very good. Now preserve them."
Jacob walked back to the desk and picked up four white note cards and a roll of scotch tape. Walking back to the board, Jacob took a piece of tape and carefully put the middle of the tape lengthwise across the first print. Holding the ends of the tape, Jacob slowly pulled the tape up, and placing it on the first note card. Jacob repeated his actions three more times, and a few minutes later, presented Grissom with four preserved prints. "Why do we preserve prints?"
"Sir we preserve prints so that we can compare them to other prints and look for matching characteristics. If we left them on the surfaces we found them on, we would have a very hard time comparing them, especially if they were like on a wall or something."
"Pass."