EEA FAMILY PERMIT W/ CRIME HISTORY

Hi,

I am helping my mother to apply for EEA Family member in Brazil, as I was felling the form I got to the point where the questionnaire was about convictions and other penalties, now the big question is whether to add the criminal conviction or not to add to the form.
At the time of the criminal conviction, my mother was in the UK illegally and police officer catch her with a fraudulent driving license which caused her to go to jail for 3 months, this whole situation happened 6 years ago when she was living with me in the UK. After the incident, she decided to leave the country (by her own initiative) and now she wants to come back.
If I add the details to the form I don't have much information about the court hearing and there is no paper evidence about the case. What to do? Any advice?

The conviction must be declared.