With private trackers there are some things to consider. the two biggest factors are membership count and how easy they are to get into.

The safest trackers are the ones that stay under the radar for the most part. Less than 50.000 members (Maybe even 20.000). Always closed for signup (invite or application form/interview reviewed by staff before being accepted). Other things like SSL browsing or even better SSL tracker as well as site specific torrent hashes are probably the safest ones.

But in the end as long as you are using your home line to download and share it depends on what you download. If you are worried about staying safe, then definitely invest in the added layer of security a trusted VPN or seedbox provider gives you.

I am a member on some trackers that I would say are safe. But these are old, really small <5.000 members, secured in any possible way and form and hardly accept any new members ever if any at all.