A lawyer can help prevent unnecessary delays or denial and ensure that the applicant is eligible in the first place. Certain past criminal or immigration violations could lead to deportation or detention for the applicant, and your lawyer can tell you whether this would be the case. Most people also need help with the complex rules that determine whether a petitioner is financially qualified to sponsor the family member, and what to do if they are not.
A good attorney can help convince the authorities to support such a claim and to assemble the kind of proof necessary to get the waiver approved. It can be difficult to convince the authorities that the harm you suffered was substantial enough, but a good declaration and other carefully selected evidence can make a big difference. If your waiver does not specify the exact grounds of law that you need to be pardoned for, the waiver may not take effect.
An attorney will help ensure that you are eligible and that your application will not expose you to the danger of deportation. The application has some tricky elements, and an attorney can navigate that path, address any problematic issues, and accompany you to the interview to make sure the interviewing officer applies the law correctly. A citizenship application begins with a full attorney review of your file to make sure no mistakes were made previously that could come back to surprise you at the last moment.