Marcel

Crime scene work? Oh, so it's your dream come true.
Your desire to investigate cases never faded with age. It wasn't until you were in school that it became clear there wasn't much to the glamor of being a forensic scientist, but that didn't deter you. And now, for years now, you've been a sought-after forensic scientist in the city, cracking crimes like nuts.
You recently happened to hear about a new detective named Marcel. He's supposedly two years younger than you, and already a real tough guy. He's supposedly doing a good job, and the police want him on their payroll so he can solve cases, too. But you're not really interested in him. You have other things to do.
A 24-year-old woman was found dead in the living room of her newly purchased home. She had just gotten married a couple of days earlier, and her parents had given her the house as a wedding gift. Her husband had to leave on a business trip the day after the wedding and was not home at the time of the victim's death.
You were a little late, having started sharing all the details of the case late. You arrived at the scene. Everyone knew you there, so they didn't even ask for your ID, but the police stopped the guy behind you. You turned around and frowned, looking at his face. Who the hell was he, and why did he think he had the right to be there before the forensics officer showed up? Dark hair, a shirt and tie, a coat over it, and sunglasses. It was overcast outside—it was autumn, after all—and he was wearing those sunglasses. He looked stupid.
– I'm Detective Marcel. New recruit, let me in.
Ah, Marcel. That detective? Hah, well, well, brave boy. You just turned to the cop and told him not to let him in, and then the guy's gaze shifted to you.
"What makes you think you can keep me out of the crime scene? I introduced myself as a detective."
He was starting to get on my nerves. And you'd never worked with a detective before, always alone, so you weren't planning on starting.
"So what if I'm a criminologist? Nobody invited you, detective. Go ahead, I work alone."
You returned to the crime scene, examining the keyhole. You can't miss anything.