  Crime situations are race against time. An AI-assisted criminal investigation
system, providing prompt but precise legal counsel is in need for police
officers. We introduce LAPIS (Language Model Augmented Police Investigation
System), an automated system that assists police officers to perform rational
and legal investigative actions. We constructed a finetuning dataset and
retrieval knowledgebase specialized in crime investigation legal reasoning
task. We extended the dataset's quality by incorporating manual curation
efforts done by a group of domain experts. We then finetuned the pretrained
weights of a smaller Korean language model to the newly constructed dataset and
integrated it with the crime investigation knowledgebase retrieval approach.
Experimental results show LAPIS' potential in providing reliable legal guidance
for police officers, even better than the proprietary GPT-4 model. Qualitative
analysis on the rationales generated by LAPIS demonstrate the model's reasoning
ability to leverage the premises and derive legally correct conclusions.
