"...you don't know what the police did or didn't do."
Yeah we do - very little.
There is no CSI here in the DR. No training on the proper collection of evidence, no collection tools/kits and no ability to deliver collected evidence to an accredited testing facility in any sort of timely manner. Chain of custody is an as yet an unheard of concept.
It is not yet a priority to fund expensive laboratories full of expensive equipment, costly consumables and well paid professionals. Advanced scientific inquiries are outsourced - to the CDC for anything related with disease, to the FDA for anything related to agriculture and pests and to the FBI for guidance on anything criminal in nature that the govt here feels the need to solve that outweighs the embarrassment of admitting they can't do it themselves - which isn't often.
The DR is a good forty years of advancement behind the current state of criminal investigations elsewhere. What happened at the Salem Witch Trials is what currently happens here. An accusation is made, a confession is extorted and someone sends the accused away or not. About the only investigative practice that is possible here are fingerprints but even that rudimentary procedure requires sampling kits and supplies that are not routinely available to the on scene police.
Most pathology reports are suspect and incomplete because of no equipment, poor sampling and storage, scant laboratory testing and a need to keep things moving as there is not sufficient storage space but for a day or two in most cases.
When it comes to tourists who are victims of crime, it is assumed that the victim will leave the island at the first possible opportunity and be very reluctant to return later to testify or offer evidence. A typical crime scene is a charlie foxtrot of police milling about looking in the bushes or pointing out blood drops to others. The investigators can usually be picked out of the crowd as they are the ones in the plaid shirts and bluejeans.
The DR does not have the means to consistently deliver justice to citizens and visitors. From the beat cop to the judges the system is broken, corrupt and rife with political interference. Try as anyone might, it just isn't possible to put together a criminal case that Perry Mason would accept. It is clear that the police know what they should be doing in these cases but with no resources and no support from the system or the politicos to embrace forensic science and make it possible to collect, analyze and store evidence, things will not change here anytime soon.
If you are a tourist and victim of a serious or violent crime and manage to survive, leave as quickly as you can, the insult to injury only gets worse from there.