There are at least 2 phases in criminal prosecution. The first is for the purpose of determining whether there is reason to proceed to trial (ie., indict). In this phase, unsworn and hearsay evidence may be considered. Once one is indicted, only sworn evidence may be considered at trial and there is a high degree of proof required. But a court may compel persons to testify though I'm not sure how this works with a sovereign state. Pretrial investigations never "prove" matters as do trials. That is not the purpose or requirement. Having read 25% of so of Goldstone Report, I find it like an indictment lacking only findings against the individual(s) to be tried. It does not reach the level of proof required in a trial, but neither does it contain rumors, information not investigated or unsupported findings. There is only 1 Goldstone Report available to all on the UN site. It is a rigorus, professional report for the level at which it was produced.
Knesset passes 'Norwegian Law' allowing ministers to resign their seats, remain in cabinet (Haaretz)
from the article: Goldstone tells Obama: Show me flaws in Gaza report