"Sherlock, when you are examining a crime scene, please don't refer to yourself as the murderer even if it's in a hypothetical problem, people are suspicious of you enough already – they don't need any more excuses.

While I know you're just displaying your usual lack of common sense, it will cause the police to do inconvenient things. For example: arresting you, taking the body parts in the flat away as evidence, destroying your experiments and generally making themselves a nuisance.

You will be then held in a police cell for several days, get incredibly bored and be deemed as insane when you try to tell me to do something or play your violin when neither it or I are present.

It also will cause Lestrade an insane amount of paperwork which will make much less likely to offer you a case and probably end up getting Mycroft involved which you detest. Please, just think before speaking!

Also presenting the facts in a way that they seem to incriminate you, such as describing the murderer as a tall, thin, black haired man who is very intelligent and plays the violin makes the inspectors nervous and is Not a Good Thing! Please mention beforehand that said murderer isn't you; it would save time and effort.

While I'm the subject, when asked about something don't automatically say "John's my alibi" this is not only very suspicious but also drags me into whatever mess you're in and ends up with both of us in the cells.

I won't be in work again, Sarah will be worrying, Mrs Hudson will be worrying as I promised to be back tonight, Harry will … not have probably noticed – but that's not the point." John rambled as he paced the cell.

Sherlock lying on a bunk staring at the celling drawled "There is something much more important that you're totally missing, John"

"Yes, what is it?" John rounded on Sherlock.

"We're out of milk again."