"Try" means bring to trial = hear each sides' argument and reach a verdict. I'm not sure where your quote is taken from but "torture" is defined by the United Nations as 'degrading and inhuman' treatment by one party of another. You can google for the full definition. I think this is probably the most official definition available.

While in the sentence it looks like "to try" means "to test", if we could see the surrounding sentences it would probably mean "bring to court." I cannot imagine that an official convention would tell people they could torture people. "Official torture" would be torture done by someone in the government. Not torture by someone who did it just for fun. Hope this helped and I hope you can find something more pleasant to read soon :)

"try" here means initiate and conduct proceedings My best guess is that "official torture" means toture performed by some state officials (police or some other authorities)