[papertyger]

Where is there a record of a dead saint making intersession?

...and four and twenty elders fell down before the Lamb, having every one of them harps, and golden vials full of odours, which are the prayers of saints. (Rev 5:8)

[Fichori]

How do you know the saints mentioned are dead?

According to Acts 9:32, not all saints are dead.

If the saints in question are dead.

Then those prayers went from the living saints, to the dead saints, to either God, or the elders who give them to God.

That would be a direct contradiction to John 14:6

[Marysecretary]

The saints here meaning the believers on earth...