The killing of Trayvon Martin by George Zimmerman — the case where nothing makes sense, nothing —  gained greater clarity in the past couple days. The story put forth by the Sanford Police Department (SPD) and by Zimmerman “friend” Joe Oliver is starting to crumble.

The SPD video that ABC News aired last night raised serious doubts about Zimmerman’s account of a life-and-death struggle. Then, the mortician  who prepared Trayvon’s body for burial told MSNBC last night that the 17-year-old’s body didn’t show any signs of violence to support Zimmerman’s account. Now, the work of the lead detective on the Zimmerman case looms large. Justice might be blind, but she’s not dumb. And Investigator Chris Serino set out to prove it.

Serino didn’t believe Zimmerman’s version of events and recommended a manslaughter charge. But he was overruled. And according to a report from Joy-Ann Reid of the Grio yesterday, the decision came from atop the law enforcement food chain: the state attorney.

A source with knowledge of the investigation into the shooting of Trayvon Martin tells the Grio that it was then Sanford police chief Bill Lee, along with Capt. Robert O’Connor, the investigations supervisor, who made the decision to release George Zimmerman on the night of February 26th, after consulting with State Attorney Norman Wolfinger — in person.

Wolfinger told Serino that he didn’t think there was enough evidence to charge Zimmerman. According to ABC News, Serino then filed an affidavit the night of Feb. 26 stating he didn’t believe Zimmerman. And we are now finding out that Serino then set out to bring the neighborhood watch volunteer to justice.

In an interview with the Rev. Al Sharpton and later with Lawrence O’Donnell, Cheryl Brown, the mother of a 13-year-old eyewitness said that Serino told her that he didn’t believe Zimmerman’s self-defense claim.

[Serino] told me that he and the other officer with him felt that it was not self-defense and that they needed to prove it wasn’t self-defense. And he said that I needed to read between the line because there was some stereotyping going on…. I took it to mean that he felt that George Zimmerman committed this crime based on whether it’s stereotyping or racial profiling or whatever you want to call it. But those were his words. Stereotyping.

Serino was the one who recounted Zimmerman’s version of events for Tracy Martin, Trayvon’s father. Martin told us in a meeting yesterday at The Post that he asked Serino if a background check was done on Zimmerman. Yes, one was, he was told, and he was “squeaky clean.” But Martin had another question. “By Zimmerman being ‘squeaky clean,’ ” he wanted to know, “did that give him the right to shoot and kill my son?” What Martin said Serino said next fits an emerging pattern. “[H]e said it certainly didn’t. That he was going to do everything that he could do to catch this guy in a lie.”

Despite being overruled by superiors, Serino, it appears, never gave up on trying to have Zimmerman arrested. He filed that affidavit hours before delivering the tragic news to Martin and said what he would try to do. And it wasn’t until March 5 that he would pay the 13-year-old and his mother a visit. Serino felt he was onto something. And now we all know why with greater clarity than we did a week ago.