Perhaps the word "Immaculate"(adjective).
free from stain or blemish; completely neat and clean; without fault or error.
For an example, on the Kuwait news agency website they write:
The statement listed the requirements for the would-be candidates for seats in the parliament, among which being the necessity to have a Kuwaiti citizenship, be able to read and write, be at least 30 years of age, and have an immaculate criminal record.
Another example for an online job opening:
To be able to provide our clients with the best services, we are looking for men and women with:
- A background as described under 1.
- A very specific skillset as described under 2.
- The right attitude as described under 3.
- An immaculate criminal record
Or yet another example from
Malta today news papers :
'The prosecution is telling you to disbelieve a person with an immaculate criminal record and to believe a person with ten previous convictions, many of them for theft!'
Considering your example, you can tweak it little bit to say:
She/he has an immaculate criminal record.