Sine ira et studio is a Latin term meaning "without anger and fondness" or "without hate and zealousness". It was coined by Roman historian Tacitus

Tacitus

Publius Cornelius Tacitus was a senator and a historian of the Roman Empire. The surviving portions of his two major works—the Annals and the Histories—examine the reigns of the Roman Emperors Tiberius, Claudius, Nero and those who reigned in the Year of the Four Emperors...

 in the introduction to his Annals

Annals (Tacitus)

The Annals by Tacitus is a history of the reigns of the four Roman Emperors succeeding Caesar Augustus. The surviving parts of the Annals extensively cover most of the reigns of Tiberius and Nero. The title Annals was probably not given by Tacitus, but derives from the fact that he treated this...

1.1., which can be translated as follows:

The histories of Tiberius, Gaius, Claudius, and Nero, while they were in power, were falsified through terror, and after their death were written under the irritation of a recent hatred. Hence my purpose is to relate a few facts about Augustus - more particularly his last acts, then the reign of Tiberius, and all which follows, without either bitterness or partiality, from any motives to which I am far removed.

The quote is often used to remind historians, reporters, editors etc. not to get carried away by emotion when writing about war or crimes. It is also the motto of the Czech Bureau for Foreign Relations and Information and Danish Army Military Police .