one of the more fun things I learned during criminal court in Texas is that the absence of forensic evidence cannot exonerate an individual. The prosecutor and the judge covered that despite not having any forensic evidence, the jury would still be expected to be able to convict the defendant. If you weren't OK with that you weren't eligible to serve on a jury.
Was your prior assumption that forensic evidence must exist in every case—and that if it doesn’t, then there’s no way to convince a jury of someone’s guilt?
As in, as long as I clean up really well afterward, I can pretty much do what I want?
Five (or fifty-five) people giving unambiguous eyewitness testimony that clearly identified the defendant and the crime he committed, with them all keeping their stories consistent under hostile cross-examination has exactly zero forensic evidence... but if you, as a juror, found all of that persuasive, it sounds like it should be enough to convict.
They are trying to avoid a situation where you end up with one juror who watches a lot of CSI and insists that they need forensic evidence to convict, despite having a dozen eye-witnesses. If a juror cannot imagine a circumstance where the evidence could be beyond a reasonable doubt based on non-forensic evidence, then they aren't suitable to be a juror.