I have two questions:
1: How do I formulate my statement so that I am as CLEAR as possible that I am making a justification and not an excuse.
2: What is a proper response to when someone says "Stop making excuses" even though I am making genuine justifications.
"A Justification is something you can say at a Funeral, everything else is an Excuse"
I just made that up, but it seems fitting.
In a Workplace context, how it is perceived is extremely dependent on who is listening to the information given.
Now - for an example - let's go with a simple one - 'Why were you late?' - now, a reasonable expectation to avoid being late would be to leave with sufficient time that you are 10-15 minutes early, with the maximum amount of forseeable Traffic.
Forseeable being the operative word. If you left at a reasonable time and there was a major accident where all the arterial roads were closed - then that would be a justification.
If, however, there was just a little bit larger than normal traffic and you left at the last minute and you ended up late - that's an excuse.
In addition to this - as the severity for the failure to do the thing increases, so too does the threshold for where an excuse stops and a justification starts.
For example - if the task was fill a cup of water and the reason given was 'the water cooler was empty' - who cares? it's a justification.
Now, take the same task, only - it's not just a cup of water - it's that you need to top up the coolant of with a cup of water for a critical bit of machinery, otherwise it will blow up and kill lots of people - would 'Oh the Watercooler is empty' cut it? Of course not. Since the severity is greater, the amount of effort is greater too - so you'd expect someone to try for a tap, go outside for a stream or river or fill it up with piss if need be.
Hence my opening statement - a Justification is something you can say at a Funeral, everything else is an Excuse.
Finally - to address the 2 questions directly:
If you are providing a Justification, you just state what happened - Simple facts - X, Y and Z.
Unfortunately - if someone tells you 'Stop making Excuses' - your best recourse at that point is 'Understood' and leave it at that. If you've reached the point in the conversation where they say that, there's nothing else you can say as it won't be listened to anyway.
Sometimes, you have to take it on the Chin and suck it up, even if there may (or may not) have been legitimate factors.
See the above about severity - if your boss thinks it's important enough that you should have done more - then, there isn't much else to do.
As some additional context - I believe in many Militaries - failure to do (or not do something) is usually framed as 'You and your entire squad are now Dead' - and so there's very little that is a justification.
Theoretically, we can debate over the definition or applicability of "justification" vs "excuse", however in real life many a times this depends on the situation or context. Same statement, based on the situation can either be perceived as an excuse or a justification - there are lot of things at play here and I doubt there is a silver bullet that hits the right spot at all the times.
Rather, I'd approach this from a different angle:
Most of the time, if you try to provide a justification after the process is over, it is taken as an excuse.
On the other hand, if you keep the conversation running during the process, rather than a one-off update in the end, most of the time the chance of the justification being perceived as an excuse is lesser.
So, the key here is frequent updates, and keep the communication channel open. That way, the update is much less likely to be a surprise and have a greater chance of being accepted as a justification rather than an excuse.
Justification is when an action or inaction is made to prevent or redress something harmful.
Excuse is just a reason why something was done or not. Not necessarily to prevent or redress harm.
So in your context you need to be clear that the action/inaction was to prevent or redress something harmful.
