BloodRain
Knight of Retribution
Sherlock > L, and this Sherlock has shown to be as smart as the original iirc. They can both claim a victory, but Holmes will get there first.
Dexter's neat, maybe as neat and careful as Light. L only suspected Light because he met the characteristics of the killer [smart, in highschool, has connections to the police] and even then didn't fully believe it was him. The only suspicious things about Dexter is that he works in forensics and really enjoys bloodwork, and nothing points to those things being notable in this case. Other things like killing animals as a kid, being 'born in blood' and his 'code' about who he targets, the only things that point to Dex, were only known by his now dead dad.
There is no DNA or profiling that will point to the Butcher's identity as none of the profiling techniques will give anything close to Dexter due to vagueness and for Dexter not being that suspicions. The only thing that connects them is that one of the Butcher's victims was let off the hook due to bad blood work. Don't think Dex is named in this though.
There are two ways to catch him; Catch him in the act or finding his trophy box. Former is a difficult task on it own as half the time his targets aren't well known or even known to be criminals, and it become an even harder task as Dexter knows two professionals will be on his case. Only once from two occasions has someone found his box of slides, and it was with an obsessed character who was sure Dexter was the killer. L or Sherlock could likely find it, but they would have to be on the scene to do so, something Sherlock is more likely to do. L if he can fix some cameras up, though Dexter has been able to both realise he's been bugged and have his 6th sense triggered when someone entered his house without him knowing. Doakes found out he was the killer because of his stalker-leveled obsessed with Dex, finding out about the bad blood work, finding the box and putting a tracer on his boat. But to get to this stage they would have to suspect it was Dexter or a person like his character or profession.
Saying this again; one of the detectives will definitely be able to catch him, Im just not sure how.
Edit: 'Kay time to make the above a waste of time. Legendary FBI serial killer expert Frank Lundy got dangerously close to solving it. Snippet from a summery site:
"Agent Lundy has his team working on the assumption that the Bay Harbor Butcher is in law enforcement. Later, he, with the help of Angel and Debra, manages to narrow the search down even further: the Butcher works in that very police department. The noose tightens around Dexter's neck as Lundy uncovers some bad blood work Dexter did - deliberately bad work that led to a killer going free (which allowed Dexter the opportunity to murder him)."
Sherlock and L would probably be better at this (I say probably as Lundy has around 40 years of profiling serial killers, so may be more of an expert in this one area), so they could get to a suspect list pretty fast. Still a matter of evidence, but meh.