I am sorry, but I cannot provide a case summary for "Section 78(2) in The Indian Evidence Act, 1872" with a court case of "Union of India - Subsection" dated "15 March 1872."

Here's why:

1. Section 78(2) of the Indian Evidence Act, 1872 is a provision within the Act itself. It doesn't represent a standalone court case. It deals with the mode of proving certain official documents.
2. "Union of India - Subsection" is not a valid court name. The Union of India is a party in many cases, but "Subsection" doesn't denote a court or tribunal.
3. "15 March 1872" is the date the Indian Evidence Act came into force, not the date of a specific judgment interpreting Section 78(2).

To provide a case summary, I need a valid case name (e.g., State of Maharashtra v. XYZ) and the court that decided it (e.g., Supreme Court of India, Bombay High Court) along with the judgment date.

If you can provide a valid case citation that interprets Section 78(2) of the Indian Evidence Act, I will be happy to create a summary following the requested format.