Should we use past tense in "Lugo admitted he is the father"?

On April 13, 2009, Lugo admitted he is the father of a child conceived with Viviana Carrillo.

Boofus McGoofus got this right. I am just going to expand on his answer. The heuristic rule taught to ESL learners is that the past tense should be used for indirect quotations, as in

Lugo: "I admit I am the father of a child conceived with V.C."

Indirect quotation form:

On April 13, 2009, Lugo admitted he was the father of a child conceived with Viviana Carrillo.

But, this rule doesn't have to be applied in the case that the situation is still true, so is can be used. However, in a sentence like

On April 13, 1801, Lugo admitted he was the father of a child conceived with Viviana Carrillo.

"is" would be a little strange because both Lugo and his child are long since gone. So basically the heuristic rule can be broken in the case that the quoted fact is still true.

I would prefer "is" unless he has stopped being the father sometime since conception. While the child was conceived, he is the father.