A more thorough explanation:

impescare (im-pə-skair-ee), vb.[fr. Law French empescher “to impeach”] Hist. To impeach; to accuse.

• The king was impescared of treason by the parliament.
• The judge was impescaring the witness of perjury.

These examples illustrate the historical use of the term impescare to mean "to impeach" or "to accuse". In the first example, the parliament is accusing the king of treason, while in the second example, the judge is accusing the witness of lying under oath. Both cases involve a formal accusation of wrongdoing, which is the essence of the definition of impescare.