That's not bad MSH, but a really important point is that forensics should not be under the police umbrella.
Britain did away with that years ago. After the string of wrongful convictions in the 1970s such as the Birmingham 6, the UK reformed policing including that forensics was a separate department altogether and it's heavily against the rules to feed them info about the prosecution case you're running.
Under the old system, forensics was basically under the prosecutors department (who were also the police) so the whole thing was effectively put into action on the basis of "finding evidence to support the case" rather than finding evidence, full stop. So they already had a person in mind who they wanted to convict then the pressure was on the forensics department to "generate" evidence that would back that up. Whether or not there is openly malicious intent, such a system heavily compromises the type of results they get and the avenues of research they follow. So if the prosecutors think one guy did it, and they control the forensic investigation as well, and find someone else's fingerprints, they're much more likely to go "oh that fingerprint doesn't match, it must be bogus, keep looking" rather than treating it as a valid lead in itself. And of course if the prosecutors control the forensics then they get to decide both what gets followed up and what gets shown to the defense counsel.
So it's very important that the police just note that a crime may have been committed, then that should be pretty much where the police end of their involvement. Investigators should then come in, and they call in an independent forensics unit (who get to decide how to collect evidence), and both the prosecution and defense are developed simultaneously with equal access to the forensic evidence. The prosecution strategizing with the forensic investigators should be as illegal as tampering with a jury.