Solution: Overboard

7×7 Murdoku case · Easy · murdokuonline.org

Dylan did it — the only suspect in the room with the victim, outlined in red below.

C1C2C3C4C5C6C7
R12AnnaW3CT
R2WTTaFreya
R31TrBerndT
R44TCyrusTrTrMTr
R5EdisonTTa5
R6TMTCDylanB
R7TVictorB

Where everybody stood