db={"suspects":[{"_id":ObjectId("64f8d65249432809cdc3cb37"),"fullName":"John Doe -1","phoneNumber":"XXXXXXXXX","totalCriminalRecord":3},{"_id":ObjectId("64f8d6cd49432809cdc3cb38"),"fullName":"John Doe -2","phoneNumber":"XXXXXXXXX","totalCriminalRecord":5}],"lawyers":[{"_id":ObjectId("64f8d58849432809cdc3cb34"),"fullName":"John Doe -3","phoneNumber":"XXXXXXXXX","workAddress":"Address of .."},{"_id":ObjectId("64f8d5f349432809cdc3cb35"),"fullName":"John Doe -4","phoneNumber":"XXXXXXXXX","workAddress":"Address of .."}],"cases":[{"_id":ObjectId("64f8d9f549432809cdc3cb3d"),"crimeNumber":12345,"eventDate":"01/01/2023","suspects":[{"id":"64f8d65249432809cdc3cb37","note":"-- additional note --","lawyer":{"id":"64f8d58849432809cdc3cb34","note":"--additional note --"}},{"id":"64f8d6cd49432809cdc3cb38","note":"-- additional note --","lawyer":{"id":"64f8d58849432809cdc3cb34","note":"--additional note --"}}]}]}

db.cases.aggregate([{"$unwind":"$suspects"},{"$lookup":{"from":"suspects","let":{"suspectsIds":{"$toObjectId":"$suspects.id"}},"pipeline":[{"$match":{$expr:{"$eq":["$_id","$$suspectsIds"]}}},{"$unset":"_id"}],"as":"suspectsLookup"}},{"$unwind":"$suspectsLookup"},{"$group":{"_id":"$id",suspects:{$push:"$suspects"}}},{"$lookup":{"from":"lawyers","let":{"lawyersIds":{"$toObjectId":"$suspects.lawyer.id"}},"pipeline":[{"$match":{$expr:{"$eq":["$_id","$$lawyersIds"]}}},{"$unset":"_id"}],"as":"lawyersLookup"}},{"$unwind":"$lawyersLookup"},{"$set":{"suspects.lawyer":{"$mergeObjects":["$suspects.lawyer","$lawyersLookup"]}}},{"$set":{"suspects":[{"$mergeObjects":["$suspects","$suspectsLookup"]}]}},{"$unset":["lawyersLookup","suspectsLookup"]}])