Legal Question in Criminal Law in Missouri

Generally, a murder victims' heirs at law (spouse, children, parents, etc.) can ask for all the belongings that are not likely to be evidence in the trial of the person(s) accused or the murder. The defendant's family may not have rights to property, but the defendant and their attorney might.

Many reports are public records. Those that are can be obtained by Subpeona or formal Freedom of Information Act requests. Some can be had by going to the police station and paying the retrieval and copying costs. Most documents will be redacted (blacked out) in some places to prevent private information from being divulged.

If it has only been a year, and no arrest, then much of the information will be of an ongoing investigation fashion in the eyes of the record / evidence keepers. I do not know if they will claim that the phone is need for further investigation.

Good luck