Expired special power of attorney has no legal effect

Dear PAO,

I am planning to buy a house and lot. The person who is transacting with me bought it from the original owner, but the title of the property is still under the latter’s name. He presented to me a Special Power of Attorney for the sale of the property which was signed by the original owner. However, the Special Power of Attorney is already expired as it is indicated in the document that its validity is only one year from the date of the sale of the property to my seller. How do I go about it? How long will it take to transfer the title of the property?