When it comes to murder, the term "clearance rate" refers to those murder cases that have had a murder charge filed against a given individual, as compared to the total number of murders recorded in that jurisdiction in a given year. What muddies the water about clearance rates though, is that some jurisdictions, manipulate their clearance rate, by counting in the current year, people that are arrested for a murder that occurred in some previous year, as well as by "exceptional clearances" in which the prime suspect for the murder is no longer alive, or when necessary witnesses for successful prosecution of murder, aren't apparently available; then these are considered by those jurisdictions using such, as exceptional clearances, and hence count as murders that have been cleared. In any event, the national murder clearance rate as reported by the FBI in 1965, was just over 90%, whereas in 2015, that national rate as reported by the FBI had plummeted to just 61.5%. Further to the point, just because a given individual has been charged with the crime of murder, does not necessarily mean that they will ever be convicted of that murder, let alone tried for murder, so that, clearance rates are not the same thing as conviction rates, therefore signifying that the national clearance rate of 61.5% for murder, indicates that in all probability, perhaps 50% of those crimes classified as murder, have somebody actually convicted, ever, of that murder.
While there are all sorts of crimes that are odious, disturbing, and upsetting, it must be stated, that murder is probably the most heinous of all crimes, because a life has been wrongly taken from another person, without justification or lawful excuse. This would signify, that police departments, specifically have homicide departments for the salient reason that murder is a crime so abhorrent, that for the public safety and for its protection, that the policing arm of the state, must do all that they can do, to see that the perpetrator of any murder is caught, tried, and duly convicted. Further, every day that a given murderer is at large, is in and of itself, a menace to society, and a disgrace to justice.
One might think that with all the modern tools of this age, in regards to DNA, forensics, and the wealth of databases that can be drawn upon, that all of this would be of great aid, in increasing the murder clearance rate over time; but, in fact, the United States has regressed tremendously from the 1960s. Why is this? While there are probably a multitude of answers of various relevancy as to why this is so, the primary reason why Americas' murder clearance rate has declined precipitously, is a reflection that there are numerous enclaves within cities and communities, in which the police do not have any credibility within that area of the community, whatsoever; in which the police simply do not have either effective boots on the ground, or reliable intelligence, that allows the police to have a basic understanding of the ins and outs of that community. This reflects, in part, that the police, are seen in those communities more as agents of oppression and injustice; in addition to the rather sad fact, that police aren't terribly motivated in due diligence for murders that involve people that they don't really respect, relate to, or care about.