One person's opinion:

Litigation-Related Expenses

Administration expenses are those that are actually and necessarily incurred in the administration of the decedent’s estate; for example, for the collection of assets, payment of debts, and distribution of property. These may include legal fees incurred by the fiduciary, which are usually deductible for estate tax purposes. However, expenditures that are not essential to the settlement of the estate, but that are incurred for the individual benefit of the decedent’s heirs, may not be taken as deductions. For the expenditure to be allowable as an administration expense, it must have benefited the estate as a whole, as contrasted with the personal benefit of a beneficiary. This distinction is often difficult to make.

https://www.nyestatelitigationblog.com/2013/12/articles/probate/tax-considerations-in-will-contests/