All you can do is entering the full name or email address of the candidate into this site:
https://partnerportal.service-now.com/SearchCertificate.do
That's a public website, so you don't need to login first. There's a tricky part. If you can't find the certificate, it does not mean the candidate does not have the certificates. He/she might have used a nickname, preferred name or different email address for the certification. Ask the candidate for clarification.
I myself is an example. For some reason, some of my ServiceNow certifications are under my full name and some others under my nickname.
I hope this helps.
- Poerwantoro
