Helperough ;)
1/ Check the victims watch, 2/ Check the flush (Knife), 3/ click on gazette near toilet, 4/ click on the mirror (lipstick), 5/ Check the wastepaper basket (threat letter), 6/ On TV screen ley car keys, in drawers are cell phone battery and victims note, 7/ Under the bed you find cell phone; click on the cupboard, and from the bed take 'hair', 8/ Click on the door when TV screen is and take blood sample; click behind 'tv' and take 9mm shell 9/ Above the bed is painting, click on it, 10/ open wardrobe, click in jacket (wallet), open suitcase, 11/ Open the brifcase {f= fingerprint}. Now: Use f. brush with 'dusting agent' on the handle of knife. Then use f. tape on hand of knife, (use the same method on lipstick); use battery on cell phone; use pencil on victims note; read the thread letter; open the wallet (restaurant bill); read your personal notes.
One dot 'progress' left an I'm stuck. Eeehh...! Sorry, but you are on your own :/