Over the past eight years, I have been asked to present astronomical evidence for court cases across Australia. Typically, when we think of evidence in court, we imagine eyewitnesses, DNA, or police reports. Often, this evidence requires an expert to explain it, who is able to communicate the conclusions and data to the members of the court so that they can make an informed decision. They are usually experts in medicine, engineering, psychology, genetics... An expert in astronomy is the last thing one imagines in a court. But that's exactly what I do. Related News standard Yes Euclid Mission: in search of what no one has seen in the universe but it has to be there Judith de Jorge The European satellite will be launched from July 1 with the aim of unraveling the nature of matter and energy dark, mysterious invisible forces that seem to make up most of the universe. The first time the police asked me, it caught me a little by surprise, because I had never thought about applying astronomy in court. But after that first experience, more and more requests came, some from members of the police force itself and others from investigators who had seen my evidence in other places. Now I provide evidence as an expert for one or two cases a week. Normally it involves presenting a statement of evidence, but sometimes I am asked to appear in court and explain what it means. When they come to me it is either because the evidence they are requesting is essential to one part of the case, or the case itself is quite important and all the details are being checked and verified. But what exactly am I providing evidence for? Tracking the Sun and Moon Most of an astronomer's court tests involve calculating the positions and illumination of an astronomical body: the Sun or the Moon. Luckily, the tools we use to calculate the positions of celestial bodies are very precise, and can go back hundreds or thousands of years in the past, or project positions into the future. An obvious example is when someone claims that the Sun dazzled them at the time of a car accident. At certain times and in certain directions, in fact, the Sun can make vision difficult. An astronomer can establish where exactly the star was at the time of the incident, its position and how it aligned with the street and the direction of travel. There are also cases where someone sees something, but it happened around sunrise or sunset. It takes an expert to tell what the level of illumination was, based on the position of the Sun below the horizon. For example, what if the event occurred five minutes after sunset? It's not as easy as discerning how much light there is during the day or at night. The lighting level depends on the time of year, location and other factors. The Moon can also be judicial evidence. Especially in dark places away from city lights, an astronomer can provide evidence about how much light our satellite provided on a given night. There are also cases (or historical moments) in which people look at the view or phase of the Moon to define when something happened. A full moon has a precise definition, but the day before or after it may appear to be a full moon, even though it technically isn't. The limits of an expert astronomer Of course, as in any branch of science, there are limits to the evidence I can provide. If we talk about lighting, were there clouds covering the Moon or the Sun? And if someone were to look through a window, what would be the refraction of the window? It depends on many factors. It is up to other experts, and other parts of the legal system, to elucidate these factors. As in many other fields, space technology is providing a lot of information in law. Satellites are increasingly being used in cases to help track things as they happen. For example, space technology company Maxar operates some of the highest resolution commercial satellites for imaging the Earth. For a small fee, people can commission these satellites to observe certain areas and/or times. Lately, we have seen the impact of satellites on Russia's war in Ukraine, and how they have been instrumental in observing troop movements. They have even provided evidence of some of the alleged war crimes. Satellite images have been used in various criminal investigations, such as human trafficking or illegal mines. And in Australia, they are also being used for criminal matters, with an expert explaining the satellite images. Expert witnesses are vital Working as an expert witness has given me hope, because I have seen how hard the judicial system works to fine-tune the details, some as precise as taking into account the phase of the Moon or the position of the Sun. It is also a perfect example of role that expert voices can play in our society. In science, we actively encourage people to turn to sources of accurate and trustworthy information, especially in a time when misinformation abounds. MORE INFORMATION news No For a billion years the days lasted 19 hours... and the whole world stood still news Yes Tim White, paleoanthropologist: «We stood up when we mated. That was the beginning of our success » Thanks to experts, fields such as space and astronomy can directly influence people's lives, even in court. Desktop Code Image for mobile, amp and app Mobile code AMP code APP code This article was originally published in 'The Conversation'. ABOUT THE AUTHOR Brad E. Tucker Astrophysicist and Cosmologist. Australian National University.