Granted your opinion, I'm positive if any evidence surfaced showing JW's involvement in this crime he would be charged. It's very unusual for LE to claim someone is cleared but there it is and until something comes up, I'll accept that statement. Below is the statute of limitations for DC.
Criminal
Description Statute
Criminal
Description Statute
Kidnapping, 6 years D.C. Code § 23-113(a)(4)
Manslaughter, 6 years D.C. Code § 23-113(a)(4)
Murder, first degree, No time limit D.C. Code § 23-113(a)(1)(A)
Murder, second degree, No time limit D.C. Code § 23-113(a)(1)(A)
Kidnapping, 6 years D.C. Code § 23-113(a)(4)
Manslaughter, 6 years D.C. Code § 23-113(a)(4)
Murder, first degree, No time limit D.C. Code § 23-113(a)(1)(A)
Murder, second degree, No time limit D.C. Code § 23-113(a)(1)(A)
First, let me say I don't know if JW is involved or guilty of any crime here. If LE thinks he's guilty, given JW's work relationship with SS, and the fact that the only people who could confirm or deny certain assertions by JW are dead, makes proving it much harder than someone who didn't spend time in the S home, drive their cars and "know their business". Information that is considered suspicious by LE (and some WSers) that can be explained away with an innocent explanation is not going to be very valuable to the prosecution. The defense only needs one juror to have reasonable doubt. If LE had JW's DNA on pizza crust, I think he would not only be an official "suspect" but he would be in jail. Anything other than that or JWs fingerprints on the murder weapon in the victims' blood, can be excused with a carefully crafted story by JW and attorneys. There isn't anyone alive who can support or refute JW's degree of access to the crime scenes.
Guilty or innocent, LE will have a hard time building a case against JW unless they have his participation on video somewhere. If that was the case, I think they would have arrested him.