[mlyle]

It's my understanding that it was traced definitively to Taylor Farms, but the only positive test may have been a false positive.

You don't always get a positive test, but this doesn't necessarily prevent you from concluding the cause of food contamination.

[pudgywalsh]

> but the only positive test may have been a false positive

Software getting flagged by anti-malware as a false positive is a great way to get an evil corpo tale of woe to the top of HN with 800 points.

[dredmorbius]

Multiple chains of evidence may be used to support a conclusion. One conclusive chain is sufficient, even if others are equivocal.

You're focusing on the weakest part of the argument, which HN guidelines explicitly request you not do: <https://news.ycombinator.com/newsguidelines.html>.

(Less so if others are exculpatory. Which is not the case here. A known false positive is not conclusive proof, but neither does it explicitly clear a source.)

See for more explanation: <https://news.ycombinator.com/item?id=49044401>.