To answer your question
a bit schematically and in general terms (I am a philosopher and a psychologist, and my main interests over the last 40 years, of which I was ill 32, are logic and philosophy of science).
(0) 'Causality' is a difficult concept, and those who use it seriously and confidently rarely know much about it. A good introduction to it is "Causality", by Mario Bunge, a theoretical physicist and philosopher. It's available in Dover Paperbacks and the book to get if you want to start understanding the concept, its problems and its intricacies.
Apart from that, in ordinary standard science, to say that facts or things F are the cause of facts or things G (sex and children, no vitamine C and scurvy, cancer and death a.s.o. for resp. F and G) it is generally at least necessary that (qualified scientists have shown and published that):
(1) that facts or things F really exist
(2) that facts or things F do not come without facts or things G:
If F then probably G
(3) that facts or things G do not usually come without facts or things F:
If not F then probably not G.
In terms of intuitive probability: G is very probable or certain if F exists; G is not very probable if F does not exist; and F exists (or may be brought about, as handing out condoms, vitamine C or lemons, and anti-cancer medicines, so as to prevent resp. pregnancy, scurvy and cancer).
Furthermore, all these statements have to be validated for 'a scientific proof of causality', by reputable scientists using warranted well-tested methods and procedures, in properly designed experiments, with all research published in scientific journals, and tested and researched by qualified scientists.
That the connection between F and G then may still not be 'really causal' or the explanation while working not (quite) correct is explained by Bunge's book, but in ordinary science the above is usually sufficient for working technology and anyway often the best one has.
Finally, often a good and deep causal explanation F, such as the hypothesis of atoms, original to Democritos and Leucippos 500 B.C. (2500 years ago) is not so easy to prove, and the existence of atoms was iin fact only proven in the 20th C (though the hypothesis was used before, to provide outlines of expanations, and for generating ideas).