Relevance
At least some work resembles the project you are hiring for.
The quality level matches your expectations.
The examples demonstrate the required specialty.
The freelancer can explain why relevant decisions were made.
Ownership
The freelancer can describe their exact role.
Collaborative work is identified honestly.
Public evidence supports important claims where available.
Portfolio pieces do not appear copied or misrepresented.
Consistency
Quality is reasonably consistent.
Work history makes sense relative to claimed experience.
Several examples support the same core skill.
Current communication matches the professionalism of the portfolio.
One great image proves less than a pattern of relevant work.Look for repeated evidence that the freelancer can solve the kind of problem you have.
Ask follow-up questions
Use portfolio examples as interview material instead of treating the portfolio as a passive gallery.