What is the test for determining whether a defendant has a reasonably discernible future financial ability to pay the costs of his defense?

Section 987.8, subdivision (b), provides that where, as here, a defendant is provided legal assistance, the trial court may, after notice and a hearing, make a determination of the defendant's present ability to pay. (See also 987.8, subd. (g)(2)(B) ["Unless the court finds unusual circumstances, a defendant sentenced to state prison shall be determined not to have a reasonably discernible future financial ability to reimburse the costs of his or her defense"].) Although a trial court's finding of the defendant's present ability to pay may be implied through the content and conduct of the hearings, any finding of ability to pay must be supported by substantial evidence. (People v. Pacheco (2010) 187 Cal.App.4th 1392, 1398.)