ET confirms that Levi Johnston's mother Sherry Johnston has been sentenced to five years in jail, following her guilty plea to a drug charge stemming from her arrest last December.

Sherry's lawyer tells us she only faces two years of actual incarceration: Two of her five years were suspended, and she'll receive one year of "good time" credit as well as credit for the three months she's already served. She could possibly serve her time at home via an ankle monitor due to her lack of criminal history, her lawyer adds.

Sherry also faces three years of probation once she gets out of jail or off the ankle monitor.

Her lawyer tells ET that Levi and his sister Mercede were on hand for their mother's sentencing, and the judge called this a mitigated and unusual case. The state said they expect Sherry to do well on probation.