How can one reconvey a lien when buying a house?

The sellers are known crooks. Their house has a lien on it. I am trying to buy it. Reconveying or getting rid of the lien takes time; it is not instantaneous. When I pay the money to the escrow company, they will give me the deed and give the sellers the money at the same moment. What about the lien? If I pay for the house and lien, the crook sellers may find some way not to sell the house and get a lien cleared for them. If I pay the lienholders, the deal may not go through and I'm short of that money. Or the lienholders may not remove the lien (less likely). The house is a proposed short sale. Can the lienholders be involved with the escrow company; they turn over the lien reconveyance application and the escrow company gives them the money if escrow is closed otherwise it returns me my money and the lienholder their lien reconveyance paperwork?