They've got nothing on him. Unless they find some DNA evidence at the container, they've got two witnesses who are suspected or convicted murderers, one of whom has an interest in the outcome of the case. They've got an independant investigator who is a vicious career climber with a vendetta and multiple interests to be served by the conviction. They've got some circumstantial evidence, and another suspect with concrete evidence against him.
Let's pretend Dexter's at trial, and his lawyer is smarter than a marmot.
Counsel for the defense cross examines Estrada, the recently released mobster.
"Who did you say was pushing to get you out on parole? Maria LaGuerta? No further questions."
Counsel for the defense cross examines Hannah McKay.
"You're on trial for murder, right? You're also a suspect for the attempted murder of the defendant's adopted sister, right? I'll bet you could get a sweet deal from the District Attorney if you could serve up a bigger fish, one with a higher profile and a higher body count. No further questions."
Counsel for the defense calls ret. Capt. Tom Matthews.
"Mr. Matthews, you say you assisted Capt. LaGuerta in an investigation into the closed case of the Bay Harbor Butcher, which she conducted in her time off. Did the two of you find conclusive evidence that the defendant was not only innocent of those crimes, but that the primary suspect of the orginal investigation was, in fact, the Butcher? Did you also hear Capt. LaGuerta say that she felt compelled to clear the original primary suspect's name? You revealed details about the defendant's past to Capt. LaGuerta, according to your statement. Did that occur before or after she pushed for the early release of mr. Estrada? Thank you, mr. Matthews; nothing further."
Counsel for the defense calls Det. Allens (or officer Rubio).
"Who ordered you to follow mr. Estrada? Was Capt. LaGuerta with you when you found the shipping container with the plastic sheathing and the chainsaw? Nothing further."
Counsel for the defense calls Capt. Maria LaGuerta.
"Captain, Did you find any evidence that directly implicates the defendant in any of the BHB killings? Did you find any evidence that directly implicates the late Sgt. Doakes in any of the BHB killings? Did you push for the early release of mr. Estrada after discovering that he figures largely in the defendant's traumatic childhood? Did you order mr. Estrada to be followed to that shipping container?
Would you characterize your relationships with the members of the Morgan family as friendly? How did you respond to the promotion of Lt. Morgan? How would you characterize your relationship with the lat Sgt. Doakes? Have you ever told anyone that you felt compelled to exhonorate Sgt. Doakes? Thank you, captain; nothing further."
Closing argument for the defense:
Captain Maria LaGuerta was romantically involved with the primary suspect in the Bay Harbor Butcher killings. She admits to having a desire to clear his name. She found a convenient scapegoat in Dexter Morgan, which had the additional benefit of further damaging the reputation of Tom Matthews, with whom she had a hostile work relationship, and the career of Lt. Morgan, about whom the same could be said, especially after Mathhews promoted her to leutenant.
My client was framed by the captain for her ex-boyfriend's crimes, for the sake of advancing her own career and eliminating an up-and-coming rival on the force. Not only is there reasonable doubt that the defendant committed these crimes, but there is also sufficient evidence to prove beyond reasonable doubt that the late sargeant Doakes committed them.
