In weighing the constitutionality of a federal law, the U.S. Supreme Court sometimes gives deference to congressional findings of fact. How will it view the critical finding at the heart of its latest abortion challenge?

The justices this week will hear arguments in two cases testing the constitutionality of the federal Partial-Birth Abortion Act of 2003. Gonzales v. Carhart, No. 05-380; Gonzales v. Planned Parenthood, No. 05-1382. Partial-birth abortion is a term used for an abortion procedure, intact dilation and extraction, infrequently used in second-trimester pregnancies.