It's actually irrelevant if the are any previous incidences of intruders in the estate. OP has been a victim of crime( although I'm not sure what at this time). We lived in our previous home for 7 years and only had the one invasion. None so far in our current home. If you look at the aerial pictures of the estate as it currently is, there is a lot of building and construction going on so that tells me there will be a lot of labourers, contractors etc etc comming and going all day. Its fact that a lot of homes that are broken into are done so AFTER a homeowner has had some sort of work/renovations etc done to it. Any criminal could gain access to the estate by pretending to be with construction or even any of the workers themselves, just remaining in one of the many half built houses at the end of the day when the rest of the crews leave.
In general, as a defense for murdering someone accidentally, or proof of murdering someone on purpose, I don't know how relevant it is. In this specific case, I think it is relevant because OP's statement includes the claim that he has been victimized and this contributed to his need for firearms and his state of mind in perceiving the noise in the bathroom as a potential threat. IIRC, the prosecution countered that they found no reports of crimes against OP on file with police. I don't have the link, so if anyone remembers this differently, please chime in.
JMO.