Measuring a secured claim
A fundamental principle in dividing debts between "secured" and "unsecured" is that the amount of the secured claim is no greater than the value of the asset value to which it attachs.
Example: if the house is worth $400,000; the mortgages total 350,000; and the judgment lien is $100,000, only $50,000 of the judgment lien is a "secured claim". There is only $50,000 in equity in the house available to satisfy the lien, even though the lien's face amount is twice the available equity.
In a more complicated example, perhaps there are other assets with value to which the lien can attach, making a greater part of the lien a secured claim.
This analysis tells you how much of debt apparently represented by liens is really secured. In reorganization cases (Chapter 13 and Chapter 11), the lienholder's claim can be divided into a secured claim and an unsecured claim; the unsecured portion may be discharged.
This is also the analysis that makes huge tax liens against debtors with little or nothing less scary. Though the lien on its face is huge, the secured portion is only the value of the debtor's assets.
More discussion of tax liens.
Liens on vehicles under the "new" bankruptcy law