"Even if John is looked over as a target, the killer is way too liberal with the memory removal spells," Lestrade went on. "Sherlock freaked out majorly when he figured that out. I think that's the main reason why he washed his hands off the case."
"He doesn't want to risk John's mind," said Arthur, recalling the time a memory charm hit Sherlock at Flourish and Blott's last year. The last time he heard, Sherlock still had not recovered his lost memory, but managed to work around the absent memory to figure out what had happened (the man's genius was truly something). Either way, Sherlock had firsthand experience on what it was like to have one's memory removed. Clearly he did not wish this upon John.
"He'll sooner turn the whole island over and throw it into the Irish Sea than put John in unrecoverable danger," said Lestrade. "You wizards have too much advantage as it is. You guys only need to have one successful hit, but we can't afford to make one mistake and that's not counting our memories going caput. Not fair."
Arthur ruefully agreed. "I understand. I do wish he could at least help us figure out the clues."
"Oh, he'll be more than happy to do that. Just don't expect him to show up in the crime scenes. Or to appreciate your blood, sweat and tears. Or to think you're doing something right. Twat," Lestrade grumbled.
Arthur smiled. Clearly Mr. Lestrade had a lot of experience working with Sherlock Holmes.