I am a lawyer. In litigation there are two considerations: law and facts. The judge determines questions of law, the jury (or judge in bench trials) determines the facts (often termed the "trier of fact").
How does that work practically? A very simple example:
Let's say someone is sued for the tort of battery. It's the first tort you learn in law school. The mnemonic we learn is "IHOC" which stands for intentional harmful or offensive contact. So we now have what we call the "elements" of the tort, which must be proven individually.
1. Intentional
2. Harmful or offensive
3. Contact
This is where the question of law comes in. What does "intentional" mean? Did I intend to take the action, or did I intend to cause harm? That's a question of law that courts have determined to be that you intended harm. Did I actually have to know the harm that would result? Or maybe I just need to know that it's likely to cause some harm. Questions of law. Another potential question of law -- what does "harm" or "offensive" mean? What if the contact is with my backpack and not my body? These are issues that judges decide as questions of law.
Once we decide on the correct legal standards to apply (which is where lawyers do their most arguing and briefing), then the "trier of fact," generally a jury in the US, determines how the facts of the case fit the law. Did the defendant "intend" the harm? Did the defendant engage in "harmful or offensive" contact? Did the defendant "contact" the plaintiff? The jury decides those things based on a preponderance of the evidence in a civil case, meaning more likely than not.
In your case, you have an issue of evidence. When someone testifies, both sides get to question the witness so that the trier of fact can judge the issue and make determinations of credibility. You can testify that you kept a lot of temperatures, and you'll explain how you did it and that you have personal knowledge of what you wrote. Then the other side gets to try and poke holes in your log. Did you actually do it contemporaneous to your observations? Did you write it down the next day? How do you know your thermometer is accurate? Did you open the window just before taking the temperature? Maybe you have a history of lying to people. Then the jury gets to take your testimony in consideration. They can do with it what they like.
How does that work practically? A very simple example:
Let's say someone is sued for the tort of battery. It's the first tort you learn in law school. The mnemonic we learn is "IHOC" which stands for intentional harmful or offensive contact. So we now have what we call the "elements" of the tort, which must be proven individually.
1. Intentional 2. Harmful or offensive 3. Contact
This is where the question of law comes in. What does "intentional" mean? Did I intend to take the action, or did I intend to cause harm? That's a question of law that courts have determined to be that you intended harm. Did I actually have to know the harm that would result? Or maybe I just need to know that it's likely to cause some harm. Questions of law. Another potential question of law -- what does "harm" or "offensive" mean? What if the contact is with my backpack and not my body? These are issues that judges decide as questions of law.
Once we decide on the correct legal standards to apply (which is where lawyers do their most arguing and briefing), then the "trier of fact," generally a jury in the US, determines how the facts of the case fit the law. Did the defendant "intend" the harm? Did the defendant engage in "harmful or offensive" contact? Did the defendant "contact" the plaintiff? The jury decides those things based on a preponderance of the evidence in a civil case, meaning more likely than not.
In your case, you have an issue of evidence. When someone testifies, both sides get to question the witness so that the trier of fact can judge the issue and make determinations of credibility. You can testify that you kept a lot of temperatures, and you'll explain how you did it and that you have personal knowledge of what you wrote. Then the other side gets to try and poke holes in your log. Did you actually do it contemporaneous to your observations? Did you write it down the next day? How do you know your thermometer is accurate? Did you open the window just before taking the temperature? Maybe you have a history of lying to people. Then the jury gets to take your testimony in consideration. They can do with it what they like.
I hope that helps!