Every astrologer comes across a situation where he is given invalid data (by mistake) and accurate details about the person. It is a good self-evaluation point for the astrologer to see if he really predicts that the horoscope data is wrong.
It happened to me thrice recently. By God's grace, I have successfully figured out that the details are wrong on those occasions. Two times it was jataka charts, the other time it was an event chart. I cannot share the details of the jataka charts but I can, for an event chart.
|Chart-1 (Wrong details)|
|Chart-2 (Correct details)|
The redrawn chart (chart-2) shows a problem. Lagna lord is in the 6th house with the 6th lord being much stronger. 9th lord representing property is in 12th lord's constellation. Both 1st and 9th lords are in fiery planets' constellations. 6th lord and Ketu are in 8th lord's constellation giving a strong hint.