Talk to an immigration attorney about this situation.
In no way am I offering you legal advice, and in no way has my comment created an attorney-client relationship. You are not to rely upon my note above in any way, but insted need to sit down with counsel and share all relevant facts before receiving fully-informed legal advice. If you want to be completely sure of your rights, you must sit down with an experienced criminal defense attorney to be fully aware of your rights.
See below for an explanation of the "good moral character" requirement for US Citizenship:
"In 1996, Congress expanded the definition and type of offense considered an “aggravated felony” in the immigration context. An applicant who has been convicted of an “aggravated felony” on or after November 29, 1990, is permanently barred from establishing GMC for naturalization.
While an applicant who has been convicted of an aggravated felony prior to November 29, 1990, is not permanently barred from naturalization, the officer should consider the seriousness of the underlying offense (aggravated felony) along with the applicant's present moral character in determining whether the applicant meets the GMC requirement. If the applicant's actions during the statutory period do not reflect a reform of his or her character, then the applicant may not be able to establish GMC."
Definitely hire an immigration attorney for this, it could either way depending on the circumstances of the involuntary manslaughter, which is an "aggravated felony" for immigration purposes.
Best of luck.
The answer above is for informational purposes only and is not intended to provide legal advice or form an attorney-client relationship. The above response should not be relied upon for any specific situation. If you need legal advice specific to your needs, you should consult with a licensed attorney.