Identity of the Murderer Solution
As you have progressed through the house you have picked up a number of clues that should help you to eliminate those suspects that are innocent.
Firstly the clue on the invitation means that we know that the killer does not have brown eyes. This eliminates Mick M as he has brown eyes.
When you solved the puzzle in the wine cellar, you determined that the killer has brown hair. This eliminates Tony C as they have blond hair.
The coded message in the middle of the maze told us two things. 1. That the person who wrote it is the same age as the victim and has a younger sister and wasn't the murderer, this eliminates Simon O, and 2. That the murderer escaped upstairs to their room, so can't have been staying on the ground floor. This eliminates Billy J.
Moving on to the kitchen, and you found a mans chain that belonged to the killer. This eliminates the only female suspect Carmen D.
In the box in the dining room we found a hastily drawn up note from the victim saying that the killer was his friend. This eliminates Sam S as they are listed as an old work colleague.
In the snug we found a partial shoe print and could determine an approximate show size for the victim. We then use the conversion chart that we found later to eliminate John M as his feet were too small.
The drawers where the conversion chart was hidden was high up, and we determined that the killer must have been at least as tall as the victim. This eliminated Nick G as he is too short.
The clue in the lobby identified that the killer was not working. This again eliminated Sam S, as they are the only person who is not retired.
Once all of the above have been ruled out, only one suspect is left, and the perpetrator is Lucas Smith